Electro-optical device having two storage capacitor electrodes overlapping scanning lines

ABSTRACT

The present invention provides electro-optical device that can include, on a TFT array substrate, pixel electrodes, TFTs for switching the respective pixel electrodes, and scanning lines and data lines respectively connected to the TFTs. By laminating a capacitive electrode and a capacitive line with an interlayer insulator interposed therebetween, a storage capacitor can be formed in a region overlapping the scanning line in a plan view. This arrangement increases a pixel aperture ratio and the capacitance of the storage capacitor, thereby reducing cross-talk and ghost and presenting a high-quality image display.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to the technical field of active-matrixdriving electro-optical devices, and more particularly to the technicalfield of electro-optical devices including, in a laminate structure of asubstrate, a capacitive electrode and a capacitive line for adding acapacitor to a pixel electrode, and a thin-film transistor (TFT) forswitching a pixel.

2. Description of Related Art

Currently, in a TFT-driven active-matrix electro-optical device, when aTFT is supplied at the gate thereof with a scanning signal through ascanning line, the TFT is turned on, thereby supplying a pixel electrodethrough a source and a drain of the TFT with an image signal that isprovided through a data line to a source region of a semiconductorlayer. Since the image signal is supplied to each pixel electrodethrough each TFT for an extremely short period of time, a storagecapacitor is typically added to each pixel electrode (in parallel with acapacitor of a liquid crystal) to hold the voltage of the image signalsupplied through the TFT for a period of time substantially longer thanthe time of the on state of the TFT.

The storage capacitor is typically formed of a capacitive electrode thatis at a pixel-electrode potential and is extended from a conductivepolysilicon layer forming the drain region of the TFT connected to thepixel electrode, a dielectric layer, and a capacitive line being at apredetermined potential and including an electrode portion that isopposed to the capacitive electrode with the dielectric layer interposedtherebetween. The capacitive line is fabricated of the same conductivelayer as that forming the scanning line (a conductive polysilicon layer,for example), and is typically arranged laterally to run in parallelwith the scanning line.

SUMMARY OF THE INVENTION

There is generally a strong market demand for a higher-definitiondisplay image in electro-optical devices. To achieve higher definition,the pixel pitch can be made finer while the aperture ratio of the pixelis increased (i.e., an aperture area of the pixel through which imagelight is transmitted is expanded with respect to a non-aperture area ofeach pixel through which no image light is transmitted).

In accordance with the above-mentioned conventional art in which thescanning lines and the data lines are respectively juxtaposed in animage display area, the non-aperture area of each pixel where thescanning line and the capacitive line are arranged becomes narrower asthe aperture ratio of the fine-pitched pixel increases. As the pixelpitch becomes finer, it becomes more difficult to embed a capacitorhaving a sufficiently larger capacitance and to impart sufficientlyhigher conductivity to the scanning line and the capacitive line. When acapacitor having a sufficiently large capacitance is not available or ascanning line and a capacitive line having a sufficient conductivity isnot produced, the electro-optical device suffers from cross-talk orghosting in an image display thereof, thereby degrading the imagequality. As the aperture ratio of the fine-pitched pixels increases, thedegradation of image quality becomes more pronounced. In other words, anattempt to improve image quality creates another problem that isdifficult to resolve.

In comparison with the problem, the present invention has beendeveloped, and it is an object of the present invention to provide anelectro-optical device which increases the pixel aperture ratio whileincreasing the capacitance of a storage capacitor (or controlling areduction in the capacitance of the storage capacitor), and providing ahigh-quality image display free from cross-talk and ghosting.

To achieve the above object, the electro-optical device of the presentinvention can include, on a substrate, scanning lines and data linesthat intersect each other, thin-film transistors, each connected to oneof the scanning lines and one of the data lines, and pixel electrodesrespectively connected to the thin-film transistors. The presentinvention can also include a storage capacitor laminated above each ofthe scanning lines and including a pixel-potential capacitive electrodeconnected to the pixel electrode and being at a pixel-electrodepotential, a fixed-potential capacitive electrode at a predeterminedpotential, and a dielectric layer interposed between the pixel-potentialcapacitive electrode and the fixed-potential capacitive electrode.

In accordance with the electro-optical device of the present invention,the storage capacitor can be laminated on the scanning line (with aninterlayer insulator interposed therebetween, for example), and canincludes the pixel-potential capacitive electrode connected to the pixelelectrode and being at the pixel-electrode potential, thefixed-potential capacitive electrode at the predetermined potential, andthe dielectric layer interposed between the pixel-potential capacitiveelectrode and the fixed-potential capacitive electrode. The storagecapacitor is thus produced in a region overlapping the scanning line onthe substrate in a plan view by making use of the pixel-potentialcapacitive electrode formed in the region overlapping the scanning lineand the fixed-potential capacitive electrode opposed to thepixel-potential capacitive electrode. Unlike in the conventional art,the fixed-potential capacitive electrode (or the capacitive line) is notarranged laterally in parallel with the scanning line, and the use ofthe scanning line and the fixed-potential capacitive electrode (or thecapacitive line) does not expand the non-aperture area of each pixel,because the scanning line and the fixed-potential capacitive electrodedo not run alongside and in parallel with each other. In other words, byforming the fixed-potential capacitive electrode (or the capacitiveline) overlapping the scanning line on the substrate, the aperture areaof each pixel is expanded while a formation area of the fixed-potentialcapacitive electrode (or the capacitive line) is expanded at the sametime. The capacitance of the storage capacitor is thus relativelyincreased. A sufficiently wide line width is achieved, thereby impartingsufficient conductivity to the scanning line and the fixed-potentialcapacitive electrode (or the capacitive line). As a result, theelectro-optical device has a high aperture ratio of the fine-pitchedpixel while providing an improved image quality for a presented imagefree from cross-talk and ghost.

In one embodiment of the electro-optical device of the presentinvention, the thin-film transistor can include a gate electrode formedof part of the scanning line and located over the channel regionthereof. This embodiment provides a so-called top gate thin-filmtransistor which includes the scanning line having a storage capacitorlaminated thereon on the substrate.

In another embodiment of the electro-optical device of the presentinvention, the thin-film transistor includes a gate electrode formed ofpart of the scanning line and located below the channel region thereof.This embodiment provides a so-called bottom gate thin-film transistorwhich includes the scanning line having a storage capacitor laminatedthereon on the substrate.

In yet another embodiment of the electro-optical device of the presentinvention, the gate electrode of the thin-film transistor can be formedof the same conductive layer as the conductive layer forming thescanning line. In accordance with this embodiment, a portion of thescanning line running in a linear or comb-like configuration andfabricated of a conductive polysilicon layer, a metal layer or an alloylayer is over the gate insulator of each thin-film transistor andfunctions as a gate electrode.

In yet another embodiment of the electro-optical device of the presentinvention, the gate electrode of the thin-film transistor can be formedof a conductive layer different from the conductive layer forming thescanning line. In accordance with this embodiment, an island gateelectrode connected directly or via a contact hole to a linear scanningline fabricated of a conductive polysilicon layer, a metal layer or analloy layer is arranged on the gate insulator of each thin-filmtransistor. The material of the gate electrode is a conductivepolysilicon layer, a metal layer, or an alloy layer.

In still another embodiment of the electro-optical device of the presentinvention, the storage capacitor is located over the scanning line onthe substrate. In accordance with this embodiment, a formation area ofthe storage capacitor is expanded making use of a non-aperture areaoverlapping the scanning line.

In still another embodiment of the electro-optical device of the presentinvention, the storage capacitor is located below the scanning line onthe substrate. In accordance with this embodiment, a formation area ofthe storage capacitor is expanded making use of a non-aperture areaunderlapping the scanning line.

In still another embodiment of the electro-optical device of the presentinvention, the storage capacitor is located in an interlayer positionover the data line on the substrate. In accordance with this embodiment,the storage capacitor is located in the interlayer position over thedata line on the substrate, and a formation area of the storagecapacitor is expanded by making use of a non-aperture area overlappingthe scanning line.

In still another embodiment of the electro-optical device of the presentinvention, the storage capacitor is located in an interlayer positionbetween the data line and the scanning line on the substrate. Inaccordance with this embodiment, the storage capacitor is located in theinterlayer position between the data line and the scanning line on thesubstrate, and a formation area of the storage capacitor is expanded bymaking use of a non-aperture area overlapping the scanning line.

In still another embodiment of the electro-optical device of the presentinvention, one of the fixed-potential capacitive electrode and thepixel-potential capacitive electrode is formed of the same conductivelayer as the conductive layer forming the data line. In accordance withthis embodiment, the storage capacitor having the capacitive electrodefabricated of the same conductive layer as the conductive layer formingthe data line, for example, fabricated of Al (aluminum), is produced ina non-aperture area overlapping the scanning line.

In still another embodiment of the electro-optical device of the presentinvention, the pixel-potential capacitive electrode is located over thefixed-potential capacitive electrode. Since the pixel-potentialcapacitive electrode is located over the fixed-potential capacitiveelectrode in accordance with this embodiment, one of the pixel electrodeand the thin-film transistor is electrically connected to thepixel-potential capacitive electrode via a contact hole in a relativelyeasy manner.

In still another embodiment of the electro-optical device of the presentinvention, the pixel-potential capacitive electrode can be located belowthe fixed-potential capacitive electrode. Since the pixel-potentialcapacitive electrode is located below the fixed-potential capacitiveelectrode in accordance with this embodiment, the other of the pixelelectrode and the thin-film transistor is electrically connected to thepixel-potential capacitive electrode via a contact hole in a relativelyeasy manner.

In still another embodiment of the electro-optical device of the presentinvention, the interlayer position of the pixel electrode is locatedover the scanning line on the substrate. In accordance with thisembodiment, the pixel electrode arranged in the vicinity of a top layerin the laminate structure on the substrate is controlled by a thin-filmtransistor embedded in a layer therebeneath in a switching operation.

In still another embodiment of the electro-optical device of the presentinvention, the interlayer position of the pixel electrode can be locatedbelow the scanning line on the substrate. In accordance with thisembodiment, the pixel electrode arranged in the vicinity of a bottomlayer in the laminate structure on the substrate is controlled by athin-film transistor embedded in a layer thereabove in a switchingoperation.

In still another embodiment of the electro-optical device of the presentinvention, the storage capacitor can be laminated with respect to notonly the scanning line but also the data line. In accordance with thisembodiment, the fixed-potential capacitive electrode (and the capacitiveline) is laminated with respect to not only the scanning line but alsothe data line on the substrate, and the aperture area of each pixel isexpanded while the formation area of the fixed-potential capacitiveelectrode (and the capacitive line) is enlarged. The capacitance of thestorage capacitor is thus increased.

In still another embodiment, the electro-optical device of the presentinvention further includes a capacitive line which is connected to thefixed-potential capacitive electrode, is formed in a stripeconfiguration or a grid configuration and fixed to a predeterminedpotential outside an image display area.

In accordance with this embodiment, the fixed-potential capacitiveelectrode forming the storage capacitor in the image display area isfixed to the predetermined potential outside the image display area viathe capacitive line running in a stripe configuration or a gridconfiguration on the substrate. The fixed-potential capacitive electrodearranged in the image display area is reliably and relatively easilyconnected to the predetermined potential by making use of a peripheralcircuit surrounding the image display area or a constant-potential lineor a constant-potential power source for a driving circuit.

In another embodiment, the capacitive line is formed of the sameconductive layer as the conductive layer forming the fixed-potentialcapacitive electrode. In accordance with this embodiment, a portion ofthe capacitive line fabricated of a refractory metal or a polysiliconlayer, for example, running and overlapping the scanning line, islocated over the dielectric material forming each storage capacitor andfunctions as the fixed-potential capacitive electrode. In thisembodiment, the capacitive line maybe formed of a conductive layerdifferent from the conductive layer forming the fixed-potentialcapacitive electrode.

In accordance with this embodiment, an island fixed-potential capacitiveelectrode connected directly or via a contact hole to the capacitiveline, fabricated of a refractory metal layer or polysilicon layer andrunning on and overlapping the scanning line, is arranged on thedielectric layer of the storage capacitor. The fixed-potentialcapacitive electrode is formed of a refractory metal layer or apolysilicon layer, for example.

In still another embodiment of the electro-optical device of the presentinvention, the pixel-potential capacitive electrode can be formed of anisland conductive layer interposed between the thin-film transistor andthe pixel electrode. In accordance with this embodiment, thepixel-potential capacitive electrode of an island conductive layer alsofunctions as a conductive interlayer (or a barrier layer) that connectsthe thin-film transistor to the pixel electrode. In this embodiment, ajunction of the island conductive layer with the thin-film transistormay be formed in a region corresponding to the data line, a junction ofthe island conductive layer with the pixel electrode may be formed in aregion corresponding to the data line, and a junction of the islandconductive layer with the pixel electrode may be formed in a regioncorresponding to the scanning line.

With this arrangement, the junction of the island conductive layer islocated in the non-aperture area of each pixel overlapping the scanningline or the data line, and the junction does not narrow the aperturearea of the pixel.

In another embodiment, the fixed-potential capacitive electrode islaminated between the scanning line and the pixel-potential capacitiveelectrode. In accordance with this embodiment, the fixed-potentialcapacitive electrode at the predetermined potential is laminated betweenthe pixel-potential capacitive electrode at the pixel-electrodepotential and the scanning line. Variations in the potential of thepixel-potential capacitive electrode do not adversely affect thescanning line through capacitive coupling (and conversely, variations inthe potential of the scanning line do not adversely affect thepixel-potential capacitive electrode through capacitive coupling), andthe adoption of the structure in which the storage capacitor islaminated on the scanning line reduces the degradation of image quality.

In still another embodiment of the electro-optical device of the presentinvention, the pixel-potential capacitive electrode can be laminatedcloser to the scanning line than the fixed-potential capacitiveelectrode is laminated to the scanning line. The pixel-potentialcapacitive electrode with the potential thereof varying with an imagesignal can be laminated closer to the scanning line in this arrangement.However, if the interlayer insulator interposed between thepixel-potential capacitive electrode and the scanning line is set to bethicker than a predetermined value, adverse interaction throughcapacitive coupling between the pixel-potential capacitive electrode andthe scanning line is reduced in practice. The thickness of theinterlayer insulator can be determined experimentally, based onexperience, or by simulation so that the capacitive coupling isnegligibly small in the specifications of the device.

The fixed-potential capacitive electrode may be separately formed of aconductive, transparent layer (polysilicon layer, for example) or may beformed of an embedded light shielding film (a refractory metal layer)for defining the aperture area of each pixel.

In still another embodiment of the electro-optical device of the presentinvention, the fixed-potential capacitive electrode can be laminatedbetween the data line and the pixel-potential capacitive electrode.Since the fixed-potential capacitive electrode at the predeterminedpotential is laminated between the data line and the pixel-potentialcapacitive electrode at the pixel-electrode potential in accordance withthis embodiment, variations in the potential of the pixel-potentialcapacitive electrode do not adversely affect the data line throughcapacitive coupling (and conversely, variations in the potential of thedata line do not adversely affect the pixel-potential capacitiveelectrode through capacitive coupling), and the adoption of thestructure in which the storage capacitor is laminated on the data linereduces the degradation of image quality. In this embodiment, thestorage capacitor is formed not only in a region overlapping thescanning line but also a region overlapping the data line, and thecapacitance of the storage capacitor is even further increased.

In still another embodiment of the electro-optical device of the presentinvention, the pixel-potential capacitive electrode can be laminatedcloser to the data line than the fixed-potential capacitive electrode islaminated to the data line. The pixel-potential capacitive electrodewith the potential thereof varying with an image signal is laminatedcloser to the data line in this arrangement. However, if the interlayerinsulator interposed between the pixel-potential capacitive electrodeand the data line is set to be thicker than a predetermined value,adverse interaction through capacitive coupling between thepixel-potential capacitive electrode and the data line is reduced inpractice. The thickness of the interlayer insulator is determinedexperimentally, based on experience, or by simulation so that thecapacitive coupling is negligibly small in the specifications of thedevice.

In still another embodiment of the electro-optical device of the presentinvention, the fixed-potential capacitive electrode can include aportion, laminated between the scanning line and the pixel-potentialcapacitive electrode, in a region running along the scanning line on thesubstrate, and a portion, laminated between the data line and thepixel-potential capacitive electrode, in a region running along the dataline on the substrate.

In accordance with this embodiment, the fixed-potential capacitiveelectrode at the predetermined potential can be laminated between thescanning line and the pixel-potential capacitive electrode in the regionrunning along the scanning line on the substrate. In this region,therefore, an adverse effect through capacitive coupling between thescanning line and the pixel-potential capacitive electrode is reduced.Also, since the fixed-potential capacitive electrode at thepredetermined potential is laminated between the data line and thepixel-potential capacitive electrode in the region running along thedata line on the substrate, an adverse effect through capacitivecoupling between the data line and the pixel-potential capacitiveelectrode is reduced in this region.

In yet another embodiment, in the region running along the scanningline, the pixel-potential capacitive electrode is formed of one of afirst conductive layer and a second conductive layer that are laminatedwith the dielectric layer interposed therebetween while thefixed-potential capacitive electrode is formed of the other of the firstand second conductive layers. In the region running along the data line,the pixel-potential capacitive electrode is formed of the other of thefirst and second conductive layers while the fixed-potential capacitiveelectrode is formed of the one of the first and second conductivelayers.

In this arrangement, an adverse effect through capacitive couplingbetween the scanning line and the pixel-potential capacitive electrodeis reduced in the region running along the scanning line while anadverse effect through capacitive coupling between the data line and thepixel-potential capacitive electrode is reduced in the region runningalong the data line.

In still another embodiment of the electro-optical device of the presentinvention, one of the pixel-potential capacitive electrode and thefixed-potential capacitive electrode is formed of a pair of electrodesthat sandwiches the other of the pixel-potential capacitive electrodeand the fixed-potential capacitive electrode from above and from below.

Since the one of the pixel-potential capacitive electrode and thefixed-potential capacitive electrode is formed of the pair of electrodesthat sandwiches the other of the pixel-potential capacitive electrodeand the fixed-potential capacitive electrode from above and from belowin accordance with this embodiment, a storage capacitor having a largercapacitance is created with the area occupied on the substrateunchanged.

In this embodiment, the fixed-potential capacitive electrode can beformed of a pair of electrodes that sandwiches the pixel-potentialcapacitive electrode from above and from below.

Since the pixel-potential capacitive electrode at the pixel-electrodepotential is sandwiched between the pair of electrodes forming thefixed-potential capacitive electrode from above and from below,variations in the potential of the pixel-potential capacitive electrodedo not adversely affect the scanning line and the data line throughcapacitive coupling (and conversely, variations in the potential of thescanning line and the data line do not adversely affect thepixel-potential capacitive electrode through capacitive coupling), andthe adoption of the structure in which the storage capacitor islaminated on the scanning line advantageously reduces the degradation ofimage quality.

In still another embodiment of the electro-optical device of the presentinvention, at least one of the pixel-potential capacitive electrode andthe fixed-potential capacitive electrode can have a light shieldingproperty. In accordance with this embodiment, the pixel-potentialcapacitive electrode and the fixed-potential capacitive electrode havingthe light shielding property are used to prevent light from entering thethin-film transistor or from traveling through the edge area of theaperture of each pixel.

In still another embodiment of the electro-optical device of the presentinvention, the one of the capacitive electrodes having the lightshielding property contains a refractory metal. Specifically, the one ofthe capacitive electrodes is formed of a single metal layer, an alloylayer, a metal silicide layer, a polysilicide layer, or a multilayer ofthese layer, each layer fabricated of at least a refractory metalselected from the group consisting of Ti (titanium), Cr (chromium), W(tungsten), Ta (tantalum), Mo (molybdenum), and Pb (lead).

In yet another embodiment, the one of the capacitive electrodes havingthe light shielding property may be located over the thin-filmtransistor on the substrate, and may be formed of an upper lightshielding film having conductivity and at least partly defining theaperture area of each pixel.

In this arrangement, the one of the fixed-potential capacitive electrodeand the pixel-potential capacitive electrode is formed of the upperlight shielding film having conductivity and defining the aperture areaof each pixel (in other words, the embedded light shielding filmarranged over the thin-film transistor has the function of thefixed-potential capacitive electrode or the pixel-potential capacitiveelectrode in addition to the originally intended light shieldingproperty). This arrangement advantageously simplifies the laminatestructure and the manufacturing process of the device in comparison withthe case in which a dedicated conductive layer is added in a laminatestructure to form a fixed-potential capacitive electrode or apixel-potential capacitive electrode.

The upper light shielding film may be laminated between the conductivelayer forming the scanning line and the conductive layer forming thedata line, or may be laminated between the conductive layer forming thedata line and the conductive layer forming the pixel electrode.

In this case, preferably, the scanning line, the data line, and thethin-film transistor do not extend beyond the formation area of theupper light shielding film on the substrate in a plan view.

In this arrangement, no light incident on the substrate is reflectedfrom the scanning line, the data line and the thin-film transistor,because no portion of the scanning line, the data line and the thin-filmtransistor projects out of the formation area of the upper lightshielding film. This arrangement efficiently precludes the generation ofinternal reflections and multiple reflections of light in theelectro-optical device.

Preferably, the one of the capacitive electrodes having the lightshielding property covers at least the channel region of the thin-filmtransistor.

Since the one of the fixed-potential capacitive electrode and thepixel-potential capacitive electrode having the light shielding propertycovers at least the channel region of the thin-film transistor in thisarrangement, neither incident light nor returning light enters thechannel region. This arrangement effectively controls the generation ofphoto-leakage currents arising from photoelectric effect, therebypreventing a change in transistor characteristics.

In this embodiment, the one of the capacitive electrodes having thelight shielding property is located below the thin-film transistor onthe substrate, and is formed of a conductive lower light shielding filmcovering at least the channel region on the substrate if viewed from thesubstrate.

In this arrangement, the one of the fixed-potential capacitive electrodeand the pixel-potential capacitive electrode is formed of the lowerlight shielding film having conductivity at least covering the channelregion of the thin-film transistor if viewed from the substrate (i.e.,if viewed from the underside of the thin-film transistor) (in otherwords, the embedded light shielding film arranged under the thin-filmtransistor has the function of the fixed-potential capacitive electrodeor the pixel-potential capacitive electrode in addition to theoriginally intended light shielding property). This arrangementadvantageously simplifies the laminate structure and the manufacturingprocess of the device in comparison with the case in which a dedicatedconductive layer is added in a laminate structure to form afixed-potential capacitive electrode or a pixel-potential capacitiveelectrode.

The lower light shielding film may be deposited directly on thesubstrate or on an underlayer insulator formed on the substrate. In thiscase, preferably, the scanning line, the data line, and the thin-filmtransistor do not extend beyond the formation area of the lower lightshielding film on the substrate in a plan view.

In this arrangement, light reflected from the rear surface of theelectro-optical device or returning light passing through a lightsynthesizing system of a multi-panel projector composed of a pluralityof electro-optical devices is not reflected from the scanning line, thedata line and the thin-film transistor, because no portion of thescanning line, the data line and the thin-film transistor projects outof the formation area of the lower light shielding film. Thisarrangement efficiently precludes the generation of internal reflectionsand multiple reflections of light in the electro-optical device.

In still another embodiment of the present invention, theelectro-optical device includes an upper light shielding film which islocated over the thin-film transistor on the substrate and defines atleast partly the aperture area of each pixel, and a lower lightshielding film which is located below the thin-film layer on thesubstrate and covers at least the channel region of the thin-filmtransistor if viewed from the substrate, wherein the one of thecapacitive electrodes having the light shielding property is formed ofone of the upper light shielding film and the lower light shieldingfilm, and wherein the lower light shielding film does not extend beyondthe formation area of the upper light shielding film on the substrate ina plan view.

In this arrangement, the conductive upper light shielding film definingthe aperture area of each pixel and the lower light shielding filmcovering at least the channel region of the thin-film transistor arefurther arranged. The one of the capacitive electrodes having the lightshielding property is formed of one of the upper light shielding filmand the lower light shielding film. This arrangement advantageouslysimplifies the laminate structure and the manufacturing process of thedevice in comparison with the case in which a dedicated conductive layeris added in a laminate structure to form a fixed-potential capacitiveelectrode or a pixel-potential capacitive electrode. Since a light beamincident on the substrate is reflected from the lower light shieldingfilm projecting out of the formation region of the upper light shieldingfilm, the generation of internal reflections and multiple reflections oflight in the electro-optical device is effectively precluded.

In still another embodiment of the electro-optical device of the presentinvention, the pixel-potential capacitive electrode is formed of anextension of the conductive layer forming the drain region of thethin-film transistor. In accordance with this embodiment, thepixel-potential capacitive electrode is formed of the extension of theconductive layer (for example, a conductive polysilicon film) formingthe drain region of the thin-film transistor. The pixel-potentialcapacitive electrode being at the pixel electrode potential connected tothe drain region is relatively easily created.

In still another embodiment of the electro-optical device of the presentinvention, the pixel-potential capacitive electrode is formed of anextension of the conductive layer forming the pixel electrode. Inaccordance with this embodiment, the pixel-potential capacitiveelectrode can be formed of the extension of the conductive layer (forexample, an ITO (Indium Tin Oxide) film) forming the pixel electrode.The pixel-potential capacitive electrode being at the pixel electrodepotential is relatively easily created.

These and other operations and advantages of the present invention willbecome obvious from the following discussion of the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in greater detail with referenceto the following figures, wherein like numerals reference like elements,and wherein:

FIG. 1 shows an exemplary circuit of a variety of elements, and wiringsarranged in a matrix of pixels forming an image display area in theelectro-optical device of a first embodiment of the present invention;

FIG. 2 is a plan view showing a plurality of pixels mutually adjacent toeach other in a TFT array substrate having data lines, scanning lines,and pixel electrodes formed thereon in the electro-optical device of thefirst embodiment;

FIG. 3 is a cross-sectional view of the TFT array taken along line A-A′in FIG. 2;

FIG. 4 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of a second embodiment;

FIG. 5 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 4;

FIG. 6 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of a third embodiment;

FIG. 7 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 6;

FIG. 8 is a cross-sectional view of the TFT array taken along line X-X′in FIG. 6;

FIG. 9 is a cross-sectional view of the TFT array taken along line Y-Y′in FIG. 6;

FIG. 10 is a cross-sectional view of the TFT array taken along line Z-Z′in FIG. 6;

FIG. 11 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of a fourth embodiment;

FIG. 12 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 11;

FIG. 13 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of a fifth embodiment;

FIG. 14 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 13;

FIG. 15 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of a sixth embodiment;

FIG. 16 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 15;

FIG. 17 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of a seventh embodiment;

FIG. 18 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 17;

FIG. 19 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of an eighth embodiment;

FIG. 20 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 19;

FIG. 21 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of an ninth embodiment;

FIG. 22 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 21;

FIG. 23 is a plan view of a pixel of a TFT array substrate particularlyshowing an embedded light shielding film and a first light shieldingfilm in the electro-optical device of a tenth embodiment;

FIG. 24 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of an eleventh embodiment;

FIG. 25 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 24;

FIG. 26 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of a twelfth embodiment;

FIG. 27 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 26;

FIG. 28 is a cross-sectional view showing a modification of the eleventhembodiment and the twelfth embodiment;

FIG. 29 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of a thirteenth embodiment;

FIG. 30 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 29;

FIG. 31 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of a fourteenth embodiment;

FIG. 32 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 31;

FIG. 33 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of a fifteenth embodiment;

FIG. 34 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 33;

FIG. 35 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of a sixteenth embodiment;

FIG. 36 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 35;

FIG. 37 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of a seventeenth embodiment;

FIG. 38 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 37;

FIG. 39 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device of an eighteenth embodiment;

FIG. 40 is a cross-sectional view diagrammatically showing a connectionof layers through contact holes and a laminate structure forming astorage capacitor in the electro-optical device of FIG. 39;

FIG. 41 is a plan view showing of the TFT array substrate in theelectro-optical device of each embodiment with the elements formedthereon, viewed from a counter substrate; and

FIG. 42 is a cross-sectional view of the TFT array substrate taken alongline H-H′ shown in FIG. 41.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In each of the following embodiments for the purposes of discussion, theelectro-optical device of the present invention is applied to a liquidcrystal device.

The electro-optical device of a first embodiment of the presentinvention will now be discussed, referring to FIG. 1 through FIG. 3.FIG. 1 shows an exemplary circuit of a variety of elements, and wiringsarranged in a matrix of pixels forming an image display area in theelectro-optical device. FIG. 2 is a plan view showing a plurality ofpixels adjacent to each other in a TFT array substrate having datalines, scanning lines, and pixel electrodes formed thereon in theelectro-optical device. FIG. 3 is a cross-sectional view of the TFTarray taken along line A-A′ in FIG. 2. In FIG. 3, layers and members arenot necessarily drawn to scale to show the layers and members ineasy-to-identify sizes.

Referring to FIG. 1, each of a plurality of pixels arranged in a matrixforming an image display area of the electro-optical device of thisembodiment can include a pixel electrode 9 a and a TFT 30 forcontrolling the pixel electrode 9 a, and a data line 6 a to which animage signal is supplied is electrically connected to the source of theTFT 30. Image signals S1, S2, . . . , Sn may be supplied in that orderto the data lines 6 a on a one line at a time basis or may be suppliedto the data lines 6 a on a group by group basis, each group including aplurality of adjacent data lines 6 a. Scanning lines 3 a arerespectively electrically connected to the gates of the TFTs 30, and aresupplied at a predetermined timing with scanning signals G1, G2, . . . ,Gm in a pulse form in that order on a line at a time basis. The pixelelectrodes 9 a are electrically connected to the drains of the TFTs 30,and close the TFTs 30 as switching elements for a constant duration oftime, thereby writing the image signals S1, S2, . . . , Sn supplied fromthe data lines 6 a at a predetermined timing. The image signals S1, S2,. . . , Sn at a predetermined level written on the liquid crystal as oneexample of electro-optical material through pixel electrodes 9 a areheld between a counter electrode (to be discussed later) formed on acounter substrate (to be discussed later) and the pixel electrodes 9 a.

The liquid crystal modulates light to present a gradation display bychanging the orientation or order of a set of molecules with an appliedvoltage level. In the normally white mode, transmittance ratio toincident light drops in response to the applied voltage while in thenormally black mode, the transmittance ratio to the incident light risesin response to the applied voltage. The liquid-crystal display deviceoutputs light having a contrast responsive to the image signal. In orderto prevent the stored image signal from being leaked, a storagecapacitor 70 is added in parallel with the capacitance of the liquidcrystal formed between the pixel electrode 9 a and the counterelectrode. The storage capacitor 70 is formed by interposing adielectric layer between the drain of the TFT 30 and a capacitive line300 for feeding a constant voltage.

Referring to FIG. 2, the TFT array substrate of the liquid-crystaldisplay device can include a matrix of transparent pixel electrodes 9 a(with the outlines thereof represented by dotted lines 9 a′). The dataline 6 a, and the scanning line 3 a run respectively vertically andhorizontally along each pixel electrode 9 a.

The scanning line 3 a is arranged to face a channel region 1 a′ of asemiconductor layer 1 a hatched with downward inclined lines, andfunctions as a gate electrode. Arranged in each intersection of thescanning line 3 a and the data line 6 a is a pixel switching TFT 30 inwhich the scanning line 3 a is opposed to the channel region 1 a′.

In this embodiment, the capacitive line 300 overlaps the formation areaof the scanning line 3 a, as represented by solid lines in FIG. 2.Specifically, the capacitive line 300 includes a main line portion thatgenerally runs along the scanning line 3 a, a portion projecting upwardalong the data line 6 a from the intersection thereof with the data line6 a, and a neck portion having a cutout in alignment with a contact hole84. Specifically, the capacitive line 300 can be formed of a singlemetal layer, an alloy layer, a metal silicide layer, a polysilicidelayer, or a multilayer of these layer, each layer fabricated of at leasta refractory metal selected from the group including Ti, Cr, W, Ta, Mo,and Pb.

Referring to FIG. 2 and FIG. 3, the data line 6 a is electricallyconnected to a heavily doped source region 1 d of the semiconductorlayer 1 a, fabricated of a polysilicon layer, through a barrier layer303 and contact holes 81 and 82. On the other hand, the pixel electrode9 a can be electrically connected to a heavily doped drain region 1 e ofthe semiconductor layer 1 a through contact holes 83 and 84 and througha capacitive electrode 302, as a barrier layer, formed of the same layeras that forming the barrier layer 303.

Even if an interlayer distance between the pixel electrode 9 a and thesemiconductor layer 1 a forming the TFT 30 is as long as 1000 nm or so,two relatively small diameter contact holes 83 and 84 connected inseries connect the pixel electrode 9 a to the semiconductor layer 1 a inan excellent condition using the capacitive electrode 302 as a barrierlayer, in a manner free from any difficulty such as of connecting thepixel electrode 9 a and the semiconductor layer 1 a using a singlecontact hole. Accordingly, the aperture ratio of the pixel is thusincreased.

With the barrier layer employed, etching through is prevented during theopening of the contact hole. Similarly, even if an interlayer distancebetween the data line 6 a and the semiconductor layer 1 a forming theTFT 30 is long, two relatively small diameter contact holes 81 and 82connected in series connect the data line 6 a to the semiconductor layer1 a in an excellent condition using the barrier layer 303, in a mannerfree from any difficulty such as of connecting the data line 6 a and thesemiconductor layer 1 a using a single contact hole. The capacitiveelectrode 302 and the barrier layer 303 are formed of a single metallayer, an alloy layer or a metal silicide layer, each layer fabricatedof at least a refractory metal selected from the group including Ti, Cr,W, Ta, Mo, and Pb. By fabricating the capacitive electrode 302 and thebarrier layer 303 of these refractory metals, the capacitive electrode302 and the barrier layer 303 function as a light shielding filmdefining at least part of the aperture area of each pixel. Thecapacitive electrode 302 and the barrier layer 303 are producedrelatively easily by using a sputtering technique. Alternatively, thecapacitive electrode 302 and the barrier layer 303 may be fabricated ofa metal layer other than a refractory metal, may be fabricated of alight absorption layer, or may be fabricated of a conductive transparentpolysilicon layer having no light shield function, or may be fabricatedof a multi-layer composed of a plurality of these layers. At any rate,the thickness of each of the capacitive electrode 302 and the barrierlayer 303 falls within a range from 50 to 500 nm.

Referring to FIG. 2 and FIG. 3, the capacitive electrode 302 and thecapacitive line 300 are opposed to each other with a dielectric layer301 interposed therebetween, and a storage capacitor 70-1 as one exampleof the storage capacitor 70 (see FIG. 1) is formed in an areaoverlapping the scanning line 3 a and in an area overlapping the dataline 6 a in a plan view.

The capacitive line 300 extends and covers the scanning line 3 a whilecovering the capacitive electrode 302, within the formation area of thedata line 6 a, with the projecting portion thereof in a comb-likeconfiguration. The capacitive electrode 302 can be an L-shaped islandcapacitive electrode with one segment thereof extending from theintersection of the scanning line 3 a and the data line 6 a along theprojecting portion of the capacitive line 300 within the formation areaof the data line 6 a and with the other segment thereof extending alongthe capacitive line 300 within the formation area of the scanning line 3a up to the area near the adjacent data line 6 a. The storage capacitor70-1 can thus be formed in the region where the L-shaped capacitiveelectrode 302 overlaps the capacitive line 300 with the dielectric layer301 interposed therebetween.

The capacitive electrode 302, which is one electrode of the storagecapacitor 70-1, is connected to the pixel electrode 9 a via the contacthole 84 (while being connected to the heavily doped drain region 1 e viathe contact hole 83), and remains at the pixel-electrode potential.

The capacitive line 300, which includes the other electrode of thestorage capacitor 70-1, partly surrounds the image display areacontaining the pixel electrode 9 a, and is electrically connected to aconstant voltage power source to be fixed to a constant potential. Theconstant voltage power source may be a positive voltage power source ora negative voltage power source for supplying power to a scanning linedriving circuit (to be discussed in greater detail below) which suppliesthe scanning line 3 a with a scanning signal for driving the TFT 30, anda data line driving circuit (to be discussed later) for controlling asampling circuit which supplies the data line 6 a with an image signal.The constant voltage power source may be fixed to a constant voltagesupplied to the counter substrate.

The dielectric layer 301 of the storage capacitor 70-1 may be a siliconoxide layer, such as an HTO (High Temperature Oxide) layer or an LTO(Low Temperature Oxide) layer, or a silicon nitride layer, each layerhaving a relatively small thickness falling within a range from 5 to 200nm. To increase the capacitance of the storage capacitor 70-1, thethinner the dielectric layer 301 is, the better it is as long as layerreliability is assured.

Referring to FIG. 3, the electro-optical device can include atransparent TFT array substrate 10 and a transparent counter substrate20 opposed to the TFT array substrate 10. The TFT array substrate 10 isfabricated of a quartz substrate, a glass substrate, or a siliconsubstrate, for instance, and the counter substrate 20 is fabricated of aglass substrate or a quartz substrate, for instance. The TFT arraysubstrate 10 can be provided with the pixel electrodes 9 a, and arrangedon top of them is an alignment layer 16 which has been subjected to apredetermined alignment treatment such as a rubbing process. The pixelelectrode 9 a is fabricated of a transparent, conductive film, such asan ITO (Indium Tin Oxide) film. The alignment layer 16 is fabricated ofan organic thin film, such as a polyimide thin film.

The counter substrate 20 has a counter electrode (common electrode) 21extending on the entire surface thereof, and an alignment layer 22therebeneath that has been subjected to a predetermined alignmenttreatment such as a rubbing process. The counter electrode 21 isfabricated of a transparent, conductive film, such as an ITO film. Thealignment layer 22 is fabricated of an organic thin film such as apolyimide thin film.

Arranged on the TFT array substrate 10 is a pixel switching TFT 30,adjacent to each pixel electrode 9 a, for controlling switching of thepixel electrode 9 a.

Arranged on the counter substrate 20 is a second light shielding film23, as shown in FIG. 3. For this reason, incident light L1 from thecounter substrate 20 cannot enter the channel region 1 a′, a lightlydoped source region 1 b, and a lightly doped drain region 1 c of thesemiconductor layer 1 a of the pixel switching TFT 30. The second lightshielding film 23 may be provided with a highly reflective surface forreflecting the incident light L1, thereby preventing temperature fromrising in the electro-optical device.

In this embodiment, the data line 6 a having a light shielding propertyfabricated of aluminum may be used to prevent transmittance of lightinto a portion of each pixel, along the data line 6 a. The capacitiveline 300 may be fabricated of film having a light shielding property toprevent transmittance of light into the underside of the data line 6 aother than the formation area of the contact holes 81 and 82.

In this arrangement, a liquid crystal can be encapsulated in a gapsurrounded by a sealing material between the TFT array substrate 10 andthe counter substrate 20 arranged with the pixel electrodes 9 a facingthe counter electrode 21. A liquid-crystal layer 50 is thus formed. Theliquid-crystal layer 50 takes a predetermined orientation state by thealignment layer 16 and the alignment layer 22 with no electric fieldapplied by the pixel electrode 9 a. The liquid-crystal layer 50 isformed of a mixture of one or several types of nematic liquid crystals.The sealing material is an adhesive agent made of a thermal settingagent or a photo-setting agent for bonding the TFT array substrate 10 tothe counter substrate 20 along the edges thereof, and is mixed withspacers such as glass fiber or glass beads to keep a predetermineddistance between the two substrates.

An underlayer insulator 12 is arranged beneath the pixel switching TFT30. The underlayer insulator 12 is formed on the entire surface of theTFT array substrate 10, and has the function of preventing thecharacteristics of the pixel switching TFT 30 from being degraded bysurface irregularity of the TFT array substrate 10 caused during apolishing process or dirt left after a cleaning operation.

Referring to FIG. 3, the pixel switching TFT 30 has an LDD (LightlyDoped Drain) structure, and includes the scanning line 3 a, the channelregion 1 a′ of the semiconductor layer 1 a in which a channel is formedby the electric field from the scanning line 3 a, the thin insulatinglayer 2 for insulating the scanning line 3 a from the semiconductorlayer 1 a, the data line 6 a, the lightly doped source region 1 b andthe lightly doped drain region 1 c of the semiconductor layer 1 a, andthe heavily doped source region 1 d and the heavily doped drain region 1e of the semiconductor layer 1 a. A corresponding one of the pluralityof the pixel electrodes 9 a is connected to the heavily doped drainregion 1 e through the contact holes 83 and 84 and the capacitiveelectrode 302 (which functions as a capacitive electrode). Arranged onthe scanning line 3 a is a first interlayer insulator 311 in which thecontact hole 82 leading to the heavily doped source region 1 d and thecontact hole 83 leading to the heavily doped drain region 1 e areformed.

Arranged on the capacitive line 300 is a second interlayer insulator 312in which the contact hole 81 leading to the barrier layer 303 and thecontact hole 84 leading to the capacitive electrode 302 are formed.

The data line 6 a is arranged on the second interlayer insulator 312,and an interlayer insulator 7 is deposited on the data line 6 a. Thecontact hole 84 leading to the capacitive electrode 302 is formed in theinterlayer insulator 7. The above-referenced pixel electrode 9 a isformed on the interlayer insulator 7 thus constructed.

In accordance with this embodiment, the capacitive line 300 and thecapacitive electrode 302 are three-dimensionally stacked over thescanning line 3 a and the data line 6 a on the TFT array substrate. Thecapacitive line 300 extends over the scanning line 3 a while partlyprojecting over the data line 6 a. The capacitive electrode 302 extendsin the L-shaped configuration along the capacitive line 300, therebyforming the storage capacitor 70-1. Unlike the conventional art in whichthe capacitive line 300 runs alongside the scanning line 3 a, thenon-aperture area of each pixel is not expanded, and a large capacitanceof the capacitor can be obtained. With a sufficiently wide line width,the resistance of the scanning line 3 a and the capacitive line 300 islowered. Accordingly, the electro-optical device thus has a highaperture ratio of the fine-pitched pixel while providing an improvedimage quality for a presented image free from cross-talk and ghost.

In this embodiment, the capacitive electrode 302 at the pixel-electrodepotential is laminated closer to the scanning line 3 a than thecapacitive line 300 at a predetermined potential is laminated to thescanning line. For this reason, the first interlayer insulator 311interposed between the capacitive electrode 302 and the scanning line 3a is preferably as thick as 200 to 2000 nm. With the first interlayerinsulator 311 being relatively thick, an adverse effect throughcapacitive coupling between the capacitive electrode 302 and thescanning line 3 a is practically controlled. On the other hand, sincethe capacitive line 300 at the predetermined potential is laminatedbetween the capacitive electrode 302 and the data line 6 a, the dataline 6 a is advantageously free from an adverse effect throughcapacitive coupling in response to variations in the potential of thecapacitive electrode 302, and the capacitive electrode 302 (and furtherthe pixel electrode 9 a) is advantageously free from an adverse effectthrough capacitive coupling in response to variations in the potentialof the data line 6 a.

The capacitive line 300 can be formed of a light shielding film, andfurther, the capacitive electrode 302 and the barrier layer 303 may befabricated of a light shielding film. These layers may function as alight shielding film defining the aperture area of each pixel. As shownin the plan view in FIG. 2, preferably, the scanning line 3 a, the dataline 6 a, and the TFT 30 are kept within the formation area of the lightshielding film. In this arrangement, the incident light L1 entering intothe TFT array substrate 10 from above as shown in FIG. 3 is notreflected from the scanning line 3 a, the data line 6 a, and the surfaceof the TFT 30, because no portion of any of the scanning line 3 a, thedata line 6 a, and the surface of the TFT 30 projects out of the lightshielding film. The arrangement prevents the generation of internalreflections and multiple reflections of light in the electro-opticaldevice.

Although not discussed in detail in this embodiment, a lower lightshielding film (a first light shielding film 11 a shown in FIG. 7)covering the TFT 30 from the TFT array substrate 10 (from below in FIG.3) may be arranged to run in a stripe configuration along the scanningline 3 a or in a matrix along the scanning line 3 a and the data line 6a. Such a lower light shielding film blocks a returning light L2 fromthe back surface of the TFT array substrate or a projection opticalsystem, thereby preventing optical excitation due to the returning lightL2. As a result, a leakage current arising from optical excitation iscontrolled during the turning off of the TFT 30, thereby effectivelypreventing characteristics of the TFT 30 from varying. The lower lightshielding film can be formed of a single metal layer, an alloy layer, ametal silicide layer, or a polysilicide layer, each layer fabricated ofat least a refractory metal selected from the group including Ti, Cr, W,Ta, Mo, and Pb. The returning light L2 that passes through a prism fromanother electro-optical device is particularly strong in an opticalsystem such as a multi-panel color projector in which a plurality ofelectro-optical devices is combined through a prism. The use of thelower light shielding film beneath the TFT 30 is particularly useful.Like the capacitive line 300, the lower light shielding film may extendsurrounding the image display area and may be connected to a constantvoltage power source.

Although the lamination of several conductive layers forms steps on thearea along the data line 6 a and the scanning line 3 a in the embodimentdescribed above, a planarization process may be performed by grooving atrench in the TFT array substrate 10, the underlayer insulator 12, thefirst interlayer insulator 311, and the second interlayer insulator 312,and by embedding the wiring of the data line 6 a and the TFT 30 in thetrench. The steps on the interlayer insulator 7 and the secondinterlayer insulator 312 may be polished away through a CMP (ChemicalMechanical polishing) process. Alternatively, an organic SOG may be usedto planarize the laminate structure.

In the embodiment described above, the pixel switching TFT 30 preferablyhas the LDD structure shown in FIG. 3. Alternatively, the pixelswitching TFT 30 may have an offset structure in which no impurity ionimplantation is performed on the lightly doped source region 1 b and thelightly doped drain region 1 c, or may have a self-aligned type TFT inwhich a high dose impurity ion is implanted with part of the gateelectrode 3 a being used as a mask, to form heavily doped source anddrain in a self-alignment process. In this embodiment, the gateelectrode of the pixel switching TFT 30 is of a single gate structure inwhich a single gate is interposed between the heavily doped sourceregion 1 d and the heavily doped drain region 1 e, but alternatively,more than one gate electrode may be interposed therebetween. With dualgates or triple gates employed in a TFT, leakage currents in junctionsbetween the channel region and the source region and between the channelregion and the drain region are prevented, and thereby a current duringoff period is reduced.

In the electro-optical device in the first embodiment and each of thefollowing embodiments to be discussed below, the various interlayerinsulators, each interposed between conductive layers, can be fabricatedof a silicate glass film such as NSG (non-doped silicate glass), or PSG(phosphosilicate glass), a silicon nitride film, or a silicon oxidefilm, using TEOS (trimethyl phosphosilicate) gas, or TEB (triethylborate) gas or the like through an atmospheric CVD method, a reducedpressure CVD method, or a plasma CVD method.

A second embodiment of the electro-optical device of this invention willnow be discussed referring to FIG. 4 and FIG. 5. FIG. 4 is a plan viewshowing a pixel in a TFT array substrate having a data line, a scanningline, and a pixel electrode formed thereon in the electro-optical deviceof the second embodiment. FIG. 5 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor. In FIG. 5, thelayers and elements are not necessarily drawn to scale to show thelayers and members in easy-to-identify sizes and to help understand theconnection of contact holes and the laminate structure forming a storagecapacitor. In FIG. 4 and FIG. 5, elements identical to those describedwith reference to FIG. 2 and FIG. 3 (showing the first embodiment) aredesignated with the same reference numerals, and the discussion thereofis omitted.

Referring to FIG. 4 and FIG. 5, the second embodiment includes acapacitive line 300′ formed of the lower conductive layer of a storagecapacitor, instead of the capacitive electrode 302. A capacitiveelectrode 302′, instead of the capacitive line 300, can be formed of theconductive layer that is laminated on the capacitive line 300′ withdielectric layer 301 interposed therebetween. A barrier layer 303′connecting the data line 6 a to the heavily doped source region 1 d isformed of the same layer as that forming the capacitive electrode 302′.The capacitive line 300′ remains at the predetermined potential in thesame way as the capacitive line 300 in the first embodiment. Thecapacitive electrode 302′ remains at the pixel-electrode potential inthe same way as the capacitive electrode 302 in the first embodiment. Astorage capacitor 70-2 as another example of the storage capacitor 70(see FIG. 1) is thus created. The rest of the construction remains thesame as that in the first embodiment.

Unlike the conventional art in which the capacitive line 300′ runsalongside the scanning line 3 a, the second embodiment does not need theexpansion of the non-aperture area of each pixel. By laminating thecapacitive line 300′ and the capacitive electrode 302′ on the scanningline 3 a and the data line 6 a on the TFT array substrate 10, a largercapacitance of the storage capacitor results. With a sufficient linewidth employed, the resistance of the scanning line 3 a and thecapacitive line 300′ can be lowered. The electro-optical device thus hasa high aperture ratio of the fine-pitched pixel while providing animproved image quality for a presented image free from cross-talk andghosting.

In the second embodiment, the capacitive electrode 302′ is laminatedcloser to the data line 6 a than the capacitive line 300′ at apredetermined potential is laminated to the data line 6 a. For thisreason, the second interlayer insulator 312 interposed between thecapacitive electrode 302′ and the data line 6 a is preferably as thickas 200 to 2000 nm. With the second interlayer insulator 312 beingrelatively thick, an adverse effect through capacitive coupling betweenthe capacitive electrode 302′ and the data line 6 a is practicallycontrolled. On the other hand, since the capacitive line 300′ at thepredetermined potential is laminated between the capacitive electrode302′ and the scanning line 3 a, the scanning line 3 a is advantageouslyfree from an adverse effect through capacitive coupling in response tovariations in the potential of the capacitive electrode 302′, and thecapacitive electrode 302′ (and further the pixel electrode 9 a) isadvantageously free from an adverse effect through capacitive couplingin response to variations in the potential of the scanning line 3 a.

A third embodiment of the present invention is now described referringto FIG. 6 through FIG. 10. FIG. 6 is a plan view showing a pixel in aTFT array substrate having a data line, a scanning line, and a pixelelectrode formed thereon in the electro-optical device. FIG. 7 is across-sectional view diagrammatically showing a connection of layersthrough contact holes and a laminate structure forming a storagecapacitor in the electro-optical device shown in FIG. 6. FIG. 8 is across-sectional view of the TFT array taken along line X-X′ in FIG. 6.FIG. 9 is a cross-sectional view of the TFT array taken along line Y-Y′in FIG. 6. FIG. 10 is a cross-sectional view of the TFT array takenalong line Z-Z′ in FIG. 6. In FIG. 7, the layers and elements are notnecessarily drawn to scale and are changed in relative position to showthe layers and members in easy-to-identify sizes and to help understandthe connection of contact holes, and the laminate structure forming astorage capacitor. In FIG. 8 through FIG. 10, the layers and elementsare not necessarily drawn to scale to show the layers and members ineasy-to-identify sizes. Referring to FIG. 6 through FIG. 10, elementsidentical to those described with reference to FIG. 2 and FIG. 3(showing the first embodiment) are designated with the same referencenumerals, and the discussion thereof is omitted.

In the electro-optical device of the third embodiment, a storagecapacitor 70-3 includes a portion overlapping the data line 6 a and aportion overlapping the scanning line 3 a in a plan view. Theelectro-optical device of the third embodiment further includes aconductive first light shielding film 11 a arranged beneath theunderlayer insulator 12, and an embedded light shielding film 420 in theinterlayer insulator 7 (i.e., between an interlayer insulator 7 a and aninterlayer insulator 7 b).

Laminated on the TFT array substrate 10 as shown in FIG. 7 are the firstlight shielding film 11 a also serving as a capacitive line connected toa predetermined potential in the peripheral area surrounding the imagedisplay area, the underlayer insulator 12 and the TFT 30 in that order.Laminated on the TFT 30 are the first interlayer insulator 311, astorage capacitor layer, the second interlayer insulator 312, the dataline 6 a, the interlayer insulator 7 a, the embedded light shieldingfilm 420, the interlayer insulator 7 b, and the pixel electrode 9 a inthat order. The TFT 30 includes, in a channel region 1 a′ where thescanning line 3 a intersects the data line 6 a, the heavily doped sourceregion 1 d and the heavily doped drain region 1 e are formed in a regionoverlapping the data line 6.

Referring to FIG. 6 and FIG. 7, an island barrier layer 403 a extendingfrom an area near the scanning line 3 a and covering the formation areaof the data line 6 a is formed within the formation area of the dataline 6 a on the first interlayer insulator 311 as an example of thepixel-potential capacitive electrode forming the storage capacitor 70-3.The barrier layer 403 a has a portion projecting into the pixelelectrode 9 a in a plan view. An island barrier layer 403 b extendingfrom an area near the data line 6 a and covering the scanning line 3 ais formed at the same layer as that forming the barrier layer 403 a asan example of the fixed-potential capacitive electrode of the storagecapacitor 70-3. A dielectric layer 401 is formed on the barrier layer403 a, the barrier layer 403 b, and the first interlayer insulator 311.On the dielectric layer 401, an island barrier layer 404 a covering thechannel region 1 a′, the barrier layer 403 a, and the data line 6 a isformed within the formation area of the data line 6 a as thefixed-potential capacitive electrode of the storage capacitor 70-3. Thebarrier layer 404 a has a projecting portion overlapping the barrierlayer 403 b. An island barrier layer 404 b covering the barrier layer403 b and the scanning line 3 a is formed, on the scanning line 3 a, atthe same layer as that forming the barrier layer 404 a as thepixel-potential capacitive electrode of the storage capacitor 70-3. Thebarrier layer 404 b has a projecting portion that overlaps theprojecting portion of the barrier layer 403 a.

A contact hole ACNT penetrating the first interlayer insulator 311 andthe second interlayer insulator 312 conductively connects the data line6 a to the heavily doped source region 1 d.

To connect the heavily doped drain region 1 e to the pixel electrode 9a, a contact hole BCNT penetrating the first interlayer insulator 311conductively connects the heavily doped drain region 1 e to the barrierlayer 403 a. Referring to FIG. 6 and FIG. 10, a contact hole DCNTconductively connects the projecting portion of the barrier layer 403 ato the projecting portion of the barrier layer 404 b. Referring to FIG.6 and FIG. 9, a contact hole ICNT penetrating the second interlayerinsulator 312 and the interlayer insulator 7 connects the barrier layer404 b to the pixel electrode 9 a (represented by dotted line 9 a′ inFIG. 6).

To form the storage capacitor 70-3, the barrier layer 404 a isconductively connected to the first light shielding film 11 a as thecapacitive line at the predetermined potential through a contact holeSCNT penetrating the first interlayer insulator 311 and the underlayerinsulator 12. Referring to FIG. 6 and FIG. 8, a contact hole CCNTconductively connects the projecting portion of the barrier layer 404 ato the barrier layer 403 b, thereby setting the barrier layer 403 b atthe predetermined potential. The barrier layer 404 b and the barrierlayer 403 a leading to the pixel electrode 9 a are set to thepixel-electrode potential.

In the third embodiment, the storage capacitor 70-3 is partly formed ofthe barrier layer 403 a and the barrier layer 404 a with the dielectriclayer 401 interposed therebetween, and partly formed of the barrierlayer 403 b and the barrier layer 404 b with the dielectric layer 401interposed therebetween. The entire storage capacitor 70-3 is thusformed in the formation regions overlapping the scanning line 3 a andthe data line 6 a. The first light shielding film 11 a functions as acapacitive line to be fixed to a predetermined potential near the imagedisplay area while having the function of preventing the light returningfrom the TFT array substrate 10 from entering the semiconductor layer 1a of the TFT 30.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the third embodiment does not need the expansion ofthe non-aperture area of each pixel. By laminating the capacitive lineand the capacitive electrode on the scanning line and the data line onthe TFT array substrate, a larger capacitance of the storage capacitorresults. With a sufficiently wide line width employed, the resistance ofthe scanning line and the capacitive line can be lowered. Theelectro-optical device thus has a high aperture ratio of thefine-pitched pixel while providing an improved image quality for apresented image free from cross-talk and ghosting.

In accordance with the third embodiment, the conductive electrodeforming the pixel-potential capacitive electrode and the conductivelayer forming the fixed-potential capacitive electrode are reversed inthe region running along the scanning line 3 a and in the region runningalong the data line 6 a. Specifically, since the barrier layer 403 b atthe predetermined potential is laminated between the barrier layer 404 bat the pixel-electrode potential and the scanning line 3 a within themajor portion of the area along the scanning line 3 a, the scanning line3 a is free from an adverse effect through capacitive coupling arisingfrom variations in the potential of the barrier layer 404 b, and thebarrier layer 404 b (and the pixel electrode 9 a) is free from anadverse effect through capacitive coupling arising from variations inthe potential of the scanning line 3 a. At the same time, since thebarrier layer 404 a at the predetermined potential is laminated betweenthe barrier layer 403 a at the pixel-electrode potential and the dataline 6 a within the major portion of the area along the data line 6 a,the data line 6 a is free from an adverse effect through capacitivecoupling arising from variations in the potential of the barrier layer403 a, and the barrier layer 403 a (and the pixel electrode 9 a) is freefrom an adverse effect through capacitive coupling arising fromvariations in the potential of the data line 6 a.

In the third embodiment, the capacitive line can be formed of the firstlight shielding film 11 a which runs in a stripe configuration or in agrid configuration on the TFT array substrate 10 and which isrespectively fixed to the island barrier layer 403 b and the islandbarrier layer 404 a formed for each pixel on the TFT array substrate 10.The capacitive line is thus connected to the predetermined potentialthrough the first light shielding film 11 a outside the image displayarea. Taking advantage of a constant voltage line or a constant voltagepower source outside the image display area, the capacitive line wiredwithin the image display area is relatively easily and reliably set tothe predetermined potential.

Like the capacitive electrode 302 and the barrier layer 303 in the firstembodiment, the barrier layers 403 a, 403 b, 404 a, and 404 b, the firstlight shielding film 11 a, and the embedded light shielding film 420 arefabricated of a refractory metal, an alloy, a metal silicide, or amulti-layer containing these elements. The thickness of the first lightshielding film 11 a falls within a range from 5 to 200 nm. Referring toFIG. 9, a plug 6 b may be formed within the contact hole ICNT by usingthe same layer (Al film) as that forming the data line 6 a formed on thesecond interlayer insulator 312, and a plug 420 b may be formed by usingthe same layer as that forming the embedded light shielding film 420formed on the interlayer insulator 7 a. A plug may be formed in eachcontact hole by using a conductive layer in each interlayer insulator oreach contact hole may be directly connected without a plug.

A fourth embodiment of the electro-optical device of the presentinvention is described with reference to FIG. 11 and FIG. 12. FIG. 11 isa plan view showing a pixel in a TFT array substrate having a data line,a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 12 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 11. Referring to FIG. 12, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in easy-to-identify sizes and tohelp understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 11 through FIG. 12,elements identical to those described with reference to FIG. 2 and FIG.3 (showing the first embodiment) are designated with the same referencenumerals and the discussion thereof is omitted.

Referring to FIG. 11 and FIG. 12, the fourth embodiment can include apair of capacitive lines 300 a and 300 b that are connected through acontact hole 321, instead of the capacitive line 300 used in the firstembodiment. The contact hole 321 is opened in dielectric layers 301 aand 301 b near the center of the scanning line 3 a out of the formationarea of the data line 6 a in a plan view. The capacitive lines 300 a and300 b sandwich the capacitive electrode 302, thereby forming a storagecapacitor 70-4 as another example of the storage capacitor 70 (see FIG.1). The capacitive lines 300 a and 300 b run, covering the scanning line3 a, and has a projecting portion upwardly extending in a comb-likeconfiguration from the intersection thereof with the data line 6 a asshown in FIG. 11. The projecting portion of the capacitive line 300 bextends near the contact hole 83 which connects the heavily doped drainregion 1 e to the capacitive electrode 302 while the projecting portionof the capacitive line 300 b extends beyond the contact hole 83. Thecapacitive L-shaped electrode 302 is opposed to each of the capacitivelines 300 a and 300 b with the dielectric layers 301 a and 301 binterposed therebetween, thereby forming the storage capacitor 70-4. Thebarrier layer 303″ is formed of the same layer as that forming thecapacitive line 300 b, for connecting the data line 6 a to the heavilydoped source region 1 d through the contact holes 81 and 82. The rest ofthe construction of the laminate structure remains unchanged from thatof the first embodiment.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the fourth embodiment does not need the expansion ofthe non-aperture area of each pixel. By laminating the capacitive lines300 a and 300 b and the capacitive electrode 302 on the scanning line 3a and the data line 6 a on the TFT array substrate 10, a largercapacitance of the storage capacitor results.

Since the capacitive electrode 302 at the pixel-electrode potential issandwiched between the pair of capacitive lines 300 a and 300 b at thepredetermined potential from above and from below in the fourthembodiment, the scanning line 3 a and the data line 6 a are free from anadverse effect through capacitive coupling arising from variations inthe potential of the capacitive electrode 302, and the capacitiveelectrode 302 (and the pixel electrode 9 a) is free from an adverseeffect through capacitive coupling arising from variations in thepotential of the scanning line 3 a and the data line 6 a. Thisarrangement eliminates the need for thickening the first interlayerinsulator 311 and the second interlayer insulator 312 in an attempt toreduce capacitive coupling.

Referring to FIG. 13 and FIG. 14, a fifth embodiment of the presentinvention will now be described. FIG. 13 is a plan view showing a pixelin a TFT array substrate having a data line, a scanning line, and apixel electrode formed thereon in the electro-optical device. FIG. 14 isa cross-sectional view diagrammatically showing a connection of layersthrough contact holes and a laminate structure forming a storagecapacitor in the electro-optical device of FIG. 13. Referring to FIG.14, the layers and elements are not necessarily drawn to scale and arechanged in relative position to show the layers and members ineasy-to-identify sizes and to help understand the connection of contactholes, and the laminate structure forming a storage capacitor. In FIG.13 and FIG. 14, elements identical to those described with reference toFIGS. 2 and 3 (showing the first embodiment) and FIGS. 6 through 10(showing the third embodiment) are designated with the same referencenumerals and the discussion thereof is omitted.

In the electro-optical device of the fifth embodiment, the first lightshielding film 11 a on the TFT array substrate 10 is used not only as alight shielding film but also as a fixed-potential capacitive electrode.A capacitive electrode 502, which is added as a pixel-potentialcapacitive electrode, is opposed to the first light shielding film 11 awith a dielectric layer 501 interposed, as shown in FIG. 13 and FIG. 14,thereby forming a storage capacitor.

Specifically, referring to FIG. 14, the first light shielding film 11 aalso serves as a capacitive line that is connected to the predeterminedpotential in the peripheral area surrounding the image display area, andthe dielectric layer 501 and the capacitive electrode 502 are laminatedon the TFT array substrate 10 in that order. The underlayer insulator 12and the TFT 30 are laminated on the capacitive electrode 502. A barrierlayer 510 is formed at the same layer level as that for the scanningline 3 a. Laminated on the TFT 30 and the barrier layer 510 are a firstinterlayer insulator 511, the data line 6 a, the interlayer insulator 7,and the pixel electrode 9 a in that order.

The TFT 30 includes the heavily doped source region 1 d and the heavilydoped drain region 1 e in an area overlapping the data line 6 a in thechannel region 1 a′ at the intersection of the scanning line 3 a and thedata line 6 a.

The barrier layer 510 can be formed in an island within the area of thedata line 6 a adjacent to the intersection of the scanning line 3 a andthe data line 6 a. The barrier layer 510 has a portion projecting intothe area of the pixel electrode 9 a in a plan view.

A contact hole 551 penetrating the first interlayer insulator 511connects the heavily doped source region 1 d to the data line 6 a.

To connect the heavily doped drain region 1 e to the pixel electrode 9a, first, a contact hole 554 conductively connects the heavily dopeddrain region 1 e to the barrier layer 510. Then, a contact hole 553penetrating the first interlayer insulator 511 and the interlayerinsulator 7 conductively connects the projecting portion of the barrierlayer 510 to the pixel electrode 9 a.

To form a storage capacitor 70-5, the first light shielding film 11 aextends along the scanning line 3 a and the data line 6 a in a matrix,and is connected to the predetermined potential. The capacitiveelectrode 502 is an L-shaped island capacitive electrode with onesegment thereof extending from the intersection of the scanning line 3 aand the data line 6 a along the first light shielding film 11 a withinthe formation area of the data line 6 a and with the other segmentthereof extending along the first light shielding film 11 a within theformation area of the scanning line 3 a. The capacitive electrode 502 isconductively connected to the barrier layer 510 through a contact hole555 penetrating the underlayer insulator 12, and is thus connected tothe pixel-electrode potential. In this way, the first light shieldingfilm 11 a is opposed to the L-shaped capacitive electrode 502 with thedielectric layer 501 interposed therebetween, thereby forming thestorage capacitor 70-5.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the fifth embodiment does not need the expansion ofthe non-aperture area of each pixel. By laminating the capacitive line(the first light shielding film 11 a) and the capacitive electrode 502on the scanning line 3 a and the data line 6 a on the TFT arraysubstrate 10, a larger capacitance of the storage capacitor results.

Like the capacitive electrode 302 and the barrier layer 303 in the firstembodiment, the first light shielding film 11 a is fabricated of arefractory metal, an alloy, a metal silicide, or a multilayer containingthese elements, and the thickness of the first light shielding film 11 afalls within a range from 5 to 200 nm. The capacitive electrode 502 isfabricated of a conductive polysilicon layer or is a layer of the samematerial as that forming the first light shielding film 11 a, and thethickness of the capacitive electrode 502 falls within a range from 50to 100 nm. The dielectric layer 501 is a relatively thin silicon oxidelayer of HTO or LTO, or a silicon nitride film, each having a thicknessfalling within a range from 5 to 200 nm. To reduce capacitive couplingbetween the capacitive electrode 502 at the pixel-electrode potentialand the semiconductor layer 1 a, the thickness of the underlayerinsulator 12 preferably falls within a range from 200 to 2000 nm, beingrelatively thick in this embodiment.

A sixth embodiment of the electro-optical device of the presentinvention will now be described with reference to FIG. 15 and FIG. 16.FIG. 15 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 16 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 15. Referring to FIG. 16, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in easy-to-identify sizes and tohelp understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 15 and FIG. 16, elementsidentical to those described with reference to FIGS. 2 and 3 (showingthe first embodiment) and FIGS. 13 and 14 (showing the fifth embodiment)are designated with the same reference numerals, and the discussionthereof is omitted.

Referring to FIG. 15 and FIG. 16, the sixth embodiment can include acapacitive electrode 502′ beneath a first light shielding film 11 a′with a dielectric layer 501′ interposed therebetween, instead of thecapacitive electrode 502 arranged over the first light shielding film 11a with the dielectric layer 501 interposed therebetween in the fifthembodiment. A storage capacitor 70-6 as one example of the storagecapacitor 70 (see FIG. 1) is thus created. The first light shieldingfilm 11 a′ is disconnected where a contact hole 555 is arranged. Therest of the construction of the laminate structure remains unchangedfrom that of the fifth embodiment.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the sixth embodiment does not need the expansion ofthe non-aperture area of each pixel. By laminating the capacitive line(the first light shielding film 11 a) and the capacitive electrode 502′on the scanning line 3 a and the data line 6 a on the TFT arraysubstrate 10, a larger capacitance of the storage capacitor results.

In comparison with the fifth embodiment, the sixth embodiment includesthe light shielding film 11 a′ interposed between the capacitiveelectrode 502′ at the pixel-electrode potential and the semiconductorlayer 1 a. This arrangement eliminates the need for thickening theunderlayer insulator 12 in an attempt to reduce capacitive coupling.

A seventh embodiment of the electro-optical device of the presentinvention will now be described with reference to FIG. 17 and FIG. 18.FIG. 17 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 18 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 17. Referring to FIG. 18, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in easy-to-identify sizes and tohelp understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 17 and FIG. 18, elementsidentical to those described with reference to FIGS. 2 and 3 (showingthe first embodiment) and FIGS. 13 and 14 (showing the fifth embodiment)are designated with the same reference numerals, and the discussionthereof is omitted.

Referring to FIG. 17 and FIG. 18, the seventh embodiment can include,within the underlayer insulator 12 (i.e., between a first underlayerinsulator 12 a and a second underlayer insulator 12 b), a capacitiveelectrode 602 and a conductive layer 603 with a dielectric layer 601interposed therebetween, instead of the first light shielding film 11 aand the capacitive electrode 502 with the dielectric layer 501interposed therebetween in the fifth embodiment. A storage capacitor70-7 as one example of the storage capacitor 70 (see FIG. 1) is thuscreated. The capacitive electrode 602 is connected to the barrier layer510 via a contact hole 655, and is set to the pixel-electrode potential.On the other hand, the conductive layer 603 is connected to the firstlight shielding film 11 a via a contact hole 656, and is set to thepredetermined potential. Each of the pair of the capacitive electrode602 and the conductive layer 603 has an L-shaped configuration in a planview with one segment of the L-shaped configuration extending along thescanning line 3 a and with the other segment extending along the dataline 6 a. The segment of the conductive layer 603 extending along thedata line 6 a runs up to near the contact hole 655 that connects thebarrier layer 510 and the capacitive electrode 602, and the segment ofthe capacitive electrode 602 extending along the data line 6 a runsbeyond the contact hole 655. On the other hand, the segment of theconductive layer 603 extending along the scanning line 3 a runs beyondthe contact hole 656 that connects the conductive layer 603 to the firstlight shielding film 11 a, and the segment of the capacitive electrode602 extending along the scanning line 3 a runs up to near the contacthole 656. The rest of the construction of the laminate structure remainsunchanged from that of the fifth embodiment.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the seventh embodiment does not need the expansion ofthe non-aperture area of each pixel. By laminating the capacitive lineand the capacitive electrode on the scanning line 3 a and the data line6 a on the TFT array substrate 10, a larger capacitance of the storagecapacitor results.

Although the storage capacitor 70-7 is created between the first lightshielding film 11 a and the TFT 30 in the seventh embodiment, thestorage capacitor 70-7 may be formed between the first light shieldingfilm 11 a and the TFT array substrate 10.

When the storage capacitor 70 is formed beneath the semiconductor layer1 a in the fifth embodiment through the seventh embodiment as describedabove, a portion of the semiconductor layer 1 a extending from thesemiconductor layer 1 e may be used as a capacitive electrode inaddition to or instead of the capacitive electrode.

In accordance with the third embodiment, and the fifth embodimentthrough the seventh embodiment, the first light shielding film 11 aarranged beneath the semiconductor layer 1 a has the function of thecapacitive line in addition to the originally intended light shieldingfunction, and the laminate structure and the manufacturing processthereof are substantially simplified. When the first light shieldingfilm 11 a is arranged in this way, the scanning line 3 a, the data line6 a, and the TFT 30 are preferably kept to within the formation area ofthe first light shielding film 11 a in a plan view. In this arrangement,no returning light is reflected from the scanning line 3 a, the dataline 6 a and the TFT 30, because no portion of the scanning line 3 a,the data line 6 a and the TFT 30 projects out of the formation area ofthe first light shielding film 11 a. This arrangement efficientlyprecludes the generation of internal reflections and multiplereflections of light in the electro-optical device.

An eighth embodiment of the electro-optical device of this inventionwill now be described with reference to FIG. 19 and FIG. 20. FIG. 19 isa plan view showing a pixel in a TFT array substrate having a data line,a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 20 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 19. Referring to FIG. 20, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in easy-to-identify sizes and tohelp understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 19 and FIG. 20, elementsidentical to those described with reference to FIGS. 2 and 3 (showingthe first embodiment) are designated with the same reference numerals,and the discussion thereof is omitted.

Referring to FIG. 19 and FIG. 20, the eighth embodiment can include aconductive, embedded light shielding film 700 as a capacitive line and acapacitive electrode 702 with a dielectric layer 701 interposedtherebetween, within the interlayer insulator 7 (i.e., between aninterlayer insulator 7 a and an interlayer insulator 7 b), instead ofthe capacitive line 300 and the capacitive electrode 302 with thedielectric layer 301 interposed therebetween in the first embodiment. Astorage capacitor 70-8 as an example of the storage capacitor 70 (seeFIG. 1) is thus formed. The capacitive electrode 702 is connected to thepixel electrode 9 a via a contact hole 751 penetrating the interlayerinsulator 7 b, and is set to the pixel-electrode potential. Thecapacitive electrode 702 is connected to the heavily doped drain region1 e through a contact hole 752 penetrating the interlayer insulator 7 aand a contact hole 753 penetrating the first interlayer insulator 311and through a barrier layer 705 which is fabricated of the same layer(Alfilm, for example) as that forming the data line 6 a.

The embedded light shielding film 700, defining the aperture area ofeach pixel and serving as a capacitive line of the storage capacitor70-8, extends in a grid configuration surrounding the image displayarea, and is set to the predetermined potential. The embedded lightshielding film 700 has a neck portion having a cutout in alignment withthe contact hole 751 to allow the contact hole 751 to be opened there.The capacitive electrode 702 is L-shaped in a plan view with one segmentthereof extending along the scanning line 3 a and the other segmentthereof extending along the data line 6 a. The one segment of thecapacitive electrode 702 has a wider portion around the contact hole 751to establish connection with the pixel electrode 9 a through the contacthole 751. The barrier layer 705 has a wider portion around the area ofthe contact hole 753 to be connected to the heavily doped drain region 1e via the contact hole 753. The barrier layer 705 is L-shaped in a planview to cover the opening positions of the contact hole 752 and thecontact hole 753. The data line 6 a fabricated of the same layer as thatforming the barrier layer 705 has a neck portion to be clear of thebarrier layer 705 in the area of the contact hole 753. The rest of theconstruction of the laminate structure remains unchanged from that ofthe first embodiment.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the eighth embodiment does not need the expansion ofthe non-aperture area of each pixel. By laminating the capacitive lineand the capacitive electrode on the scanning line 3 a and the data line6 a on the TFT array substrate 10, a larger capacitance of the storagecapacitor results.

The embedded light shielding film 700 and the capacitive electrode 702may be fabricated of a refractory metal, an alloy, or a metal silicideor may be a multilayer made of these materials, or may be fabricated ofthe same material as that forming the data line 6 a, for example, of Alfilm.

A ninth embodiment of the electro-optical device of the presentinvention will now be described with reference to FIG. 21 and FIG. 22.FIG. 21 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 22 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 21. Referring to FIG. 22, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in easy-to-identify sizes and tohelp understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 21 and FIG. 22, elementsidentical to those described with reference to FIGS. 2 and 3 (showingthe first embodiment) and FIGS. 19 and 20 (showing the eighthembodiment) are designated with the same reference numerals, and thediscussion thereof is omitted.

Referring to FIG. 21 and FIG. 22, in the ninth embodiment, thepositional relationship of an embedded light shielding film 700′ as acapacitive line, and a capacitive electrode 702′ with respect to adielectric layer 701′ is inverted from the positional relationship ofthe counterparts in the eighth embodiment. A storage capacitor 70-9 asanother example of the storage capacitor 70 (see FIG. 1) is thuscreated. The grid-like embedded light shielding film 700′ has a neckportion having a cutout in alignment with the contact hole 752 to allowthe contact hole 752 to be opened there in each pixel. The capacitiveelectrode 702′ is L-shaped in a plan view with one segment thereofextending along the scanning line 3 a and the other segment thereofextending along the data line 6 a. The capacitive electrode 702′ has awider portion around the contact hole 751 to establish electricallysound connection with the pixel electrode 9 a via the contact hole 751.The rest of the construction of the laminate structure remains unchangedfrom that of the eighth embodiment.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the ninth embodiment does not need the expansion ofthe non-aperture area of each pixel. By laminating the capacitive lineand the capacitive electrode on the scanning line 3 a and the data line6 a on the TFT array substrate 10, a larger capacitance of the storagecapacitor results.

When the storage capacitor 70 is formed within the interlayer insulator7 closer to the pixel electrode 9 a as in the eighth embodiment and theninth embodiment described above, the extension of the pixel electrode 9a may be used as a capacitive electrode in addition to or instead of thecapacitive electrode.

A tenth embodiment of the electro-optical device of the presentinvention will now be described with reference to FIG. 23. The tenthembodiment relates to the electro-optical device which includes anembedded light shielding film 11 a formed over the data line 6 a as inone of the eighth embodiment and the ninth embodiment, a first lightshielding film 11 a beneath the TFT 30 as in one of the thirdembodiment, and the fifth embodiment through the seventh embodiment, andthe TFT 30 and the storage capacitor 70 formed between the two lightshielding films. FIG. 23 is a plan view showing the embedded lightshielding film 1011 a and the first light shielding film 11 a in thepixels of the TFT array substrate.

In the tenth embodiment as shown in FIG. 23, the embedded lightshielding film 1011 a and the first light shielding film 11 a are formedin a grid configuration. The first light shielding film 11 a is kept tobe within the formation area of the embedded light shielding film 1011 ain a plan view (in other words, the first light shielding film 11 a isformed to be smaller than the embedded light shielding film 1011 a byone notch). The aperture area of each pixel is defined by the embeddedlight shielding film 1011 a. The scanning line, the data line, and theTFT, not shown in the drawing, interposed between the two lightshielding films are kept to within the formation area of the first lightshielding film 11 a in a plan view.

In accordance with the tenth embodiment, no incident light from thecounter substrate 20 is reflected from the first light shielding film 11a, because no portion of the first light shielding film 11 a (and, thescanning line and the data line) projects out of the formation area ofthe embedded light shielding film 1011 a. This arrangement efficientlyprecludes the generation of internal reflections and multiplereflections of light in the electro-optical device. Light returning fromthe TFT array substrate 10 may be reflected from the embedded lightshielding film 1011 a projecting out of the formation area of the firstlight shielding film 11 a, thereby causing a slight degree of internalreflections and multiple reflections of light. The returning light isfar weaker than the incident light in strength, and internal reflectionsand multiple reflections of the returning light are thus marginalcompared with those of the incident light. The arrangement of thisembodiment is thus advantageous.

The first through tenth embodiments use a top gate TFT as a pixelswitching TFT, in which the gate electrode (the scanning line) isarranged over the channel region of the semiconductor layer. In aneleventh embodiment through an eighteenth embodiment, a bottom gate TFThaving the gate electrode (the scanning line) thereof beneath thechannel region of the semiconductor layer is used as a pixel switchingTFT.

The eleventh embodiment of the electro-optical device of the presentinvention will now be discussed, referring to FIG. 24 and FIG. 25. FIG.24 is a plan view showing a pixel in a TFT array substrate having a dataline, a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 25 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 24. Referring to FIG. 25, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in easy-to-identify sizes and tohelp understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 24 and FIG. 25, elementsidentical to those described with reference to FIGS. 2 and 3 (showingthe first embodiment) are designated with the same reference numerals,and the discussion thereof is omitted.

Referring to FIG. 24 and FIG. 25, the eleventh embodiment forms astorage capacitor 70-11 as another example of the storage capacitor 70(see FIG. 1) over a bottom-gate type pixel switching TFT 30′.Specifically, a semiconductor layer 210 a is formed on a gate insulator2′ over a gate electrode that projects upward along the data line 6 a′from the scanning line 3 a′ on the TFT array substrate 10 in atooth-like configuration as shown in FIG. 24. A portion of thesemiconductor layer 210 a facing the gate electrode is called a channelregion. Arranged on the semiconductor layer 210 a are a source electrode204 a and a drain electrode 204 b, each fabricated of the same layer asthat forming the data line 6 a′ (fabricated of Al film, for example).Junction layers 205 a and 205 b of n+type a-Si (amorphous silicon) forestablishing ohmic contact are respectively laminated between thesemiconductor layer 210 a and the source electrode 204 a as well as thedrain electrode 204 b. An insulating etch stop layer 208 for protectingthe channel is formed on the semiconductor layer 210 a in the center ofthe channel region. One end of a pixel electrode 209 a is connected tothe drain electrode 204 b. An island capacitive electrode 202 islaminated on an interlayer insulator 212 formed on the end of the pixelelectrode 209 a.

A capacitive line 200 can be formed on a dielectric layer 201 laminatedon the capacitive electrode 202. The capacitive line 200 extends in astripe configuration along and beyond the image display area and is setto the predetermined potential. As shown in FIG. 24, the capacitive line200 can include a wider portion upward projecting in each pixel,covering the source electrode 204 a, the gate electrode projecting fromthe scanning line 3 a′, and the drain electrode 204 b in a plan view (inother words, the capacitive line 200 extends in a stripe configurationalong the scanning line while having a toothed portion projecting upwardin a plan view as shown in FIG. 24). On the other hand, the capacitiveelectrode 202 is connected to the end of the pixel electrode 209 athrough a contact hole 213 formed in the interlayer insulator 212 and isset to the pixel-electrode potential. The island capacitive electrode202 extends along the scanning line 3 a′ in a plan view as shown in FIG.24, while having a wider portion in alignment with the wider portion ofthe capacitive line 200 in each pixel. In this way, the eleventhembodiment includes the island capacitive electrode 202 at thepixel-electrode potential and the capacitive line 200 at thepredetermined potential with the dielectric layer 201 interposedtherebetween, thereby forming a storage capacitor 70-11 over the TFT30′.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the eleventh embodiment does not need the expansionof the non-aperture area of each pixel. By laminating the capacitiveline and the capacitive electrode on the scanning line 3 a′ and the dataline 6 a′ on the TFT array substrate 10, a larger capacitance of thestorage capacitor results.

In this embodiment, at least one of the capacitive line 200 and thecapacitive electrode 202 is fabricated of a conductive, light shieldingfilm, and functions as an embedded light shielding film defining theaperture area of each pixel. At least one of the capacitive line 200 andthe capacitive electrode 202 is fabricated of a conductive, transparentlayer, and an embedded light shielding film defining the aperture areaof each pixel may be separately formed.

A twelfth embodiment of the electro-optical device of the presentinvention will now be described with reference to FIG. 26 and FIG. 27.FIG. 26 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 27 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 26. Referring to FIG. 27, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in easy-to-identify sizes and tohelp understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 26 and FIG. 27, elementsidentical to those described with reference to FIGS. 24 and 25 (showingthe eleventh embodiment) are designated with the same reference numeralsand the discussion thereof is omitted.

Referring to FIG. 26 and FIG. 27, the twelfth embodiment can include apair of capacitive lines 200 a and 200 b with the capacitive electrode202 interposed therebetween, instead of a single capacitive line 200used in the eleventh embodiment. A storage capacitor 70-12 as anotherexample of the storage capacitor 70 (see FIG. 1) is thus formed. In aplan view in FIG. 26, each of the capacitive lines 200 a and 200 b has awider portion or a projecting portion in each pixel in an upwarddirection in FIG. 26, covering not only the source electrode 204 b, thegate electrode projecting from the scanning line 3 a′, and the drainelectrode 204 b but also the data line 6 a′ (in other words, each of thecapacitive lines 200 a and 200 b extends in a stripe configurationhaving a large tooth projecting upward). On the other hand, the islandcapacitive electrode 202 has a wider portion upward projecting in FIG.26 (namely, has an L-shaped configuration with the inner corner thereofstepwise expanding). The pair of the capacitive lines 200 a and 200 b atthe predetermined potential may be connected to each other throughcontact holes on a per pixel or per group, or may be independentlyrouted in a stripe configuration up to the outside of the image displayarea and connected to separate constant voltage power sources. The restof the construction of the laminate structure remains unchanged fromthat of the eleventh embodiment.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the twelfth embodiment does not need the expansion ofthe non-aperture area of each pixel. By laminating the capacitive lines200 a and 200 b, and the capacitive electrode 202 on the scanning line 3a′ and the data line 6 a′ on the TFT array substrate 10, a largercapacitance of the storage capacitor results.

In accordance with the twelfth embodiment, the capacitive electrode 202at the pixel-electrode potential is sandwiched between the pair ofcapacitive lines 200 a and 200 b at the predetermined potential fromabove and below. The scanning line 3 a′ and the data line 6 a′ are freefrom an adverse effect through capacitive coupling arising fromvariations in the potential of the capacitive electrode 202, and thecapacitive electrode 202 (and the pixel electrode 209 a) is free from anadverse effect through capacitive coupling arising from variations inthe potential of the scanning line 3 a′ and the data line 6 a′. Thisarrangement eliminates the need for thickening the first interlayerinsulator 212 in an attempt to reduce capacitive coupling.

The end of the pixel electrode 209 a is positioned over thesemiconductor layer 210 a in each of the eleventh embodiment and thetwelfth embodiment, the pixel electrode 209 a may be positioned beneaththe semiconductor layer 210 a as shown in FIG. 28. In this case, thesemiconductor layer 210 a is connected to the pixel electrode 209 a by acontact hole 214 drilled in the gate insulator 2′.

A thirteenth embodiment of the electro-optical device of the presentinvention will now be described with reference to FIG. 29 and FIG. 30.FIG. 29 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 30 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 29. Referring to FIG. 30, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in easy-to-identify sizes and tohelp understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 29 and FIG. 30, elementsidentical to those described with reference to FIGS. 24 and 25 (showingthe eleventh embodiment) are designated with the same referencenumerals, and the discussion thereof is omitted.

Referring to FIG. 29 and FIG. 30, in comparison with the eleventhembodiment, the thirteenth embodiment includes a pixel electrode 209 a′above a storage capacitor 70-13 as another example of the storagecapacitor 70 (see FIG. 1), and an interlayer insulator 216 laminatedbetween the capacitive line 200 and the pixel electrode 209 a′. Thepixel electrode 209 a′ is connected to the capacitive electrode 202through a contact hole 217 drilled in the interlayer insulator 216, andthe capacitive electrode 202 is thus set to the pixel-electrodepotential. The capacitive line 200 runs in a stripe configuration andhas a wide portion in each pixel (i.e., a toothed portion extendingupwardly in FIG. 29). In a plan view in FIG. 29, the capacitive line 200has one portion that the wide portion is made relatively smaller to beclear of the contact hole 217. The island capacitive electrode 202becomes slightly wider in width than the capacitive line 200 in the areaof the contact hole 217 to be connected to the contact hole 217. Therest of the construction of the laminate structure remains unchangedfrom that of the eleventh embodiment.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the thirteenth embodiment does not need the expansionof the non-aperture area of each pixel. By laminating the capacitivelines 200 and the capacitive electrode 202 on the scanning line 3 a′ andthe data line 6 a′ on the TFT array substrate 10, a larger capacitanceof the storage capacitor results.

A fourteenth embodiment of the electro-optical device of the presentinvention will now be described with reference to FIG. 31 and FIG. 32.FIG. 31 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 32 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 31. Referring to FIG. 32, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in easy-to-identify sizes and tohelp understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 31 and FIG. 32, elementsidentical to those described with reference to FIGS. 24 and 25 (showingthe eleventh embodiment) and FIGS. 29 and 30 (showing the thirteenthembodiment) are designated with the same reference numerals, and thediscussion thereof is omitted.

In comparison with the thirteenth embodiment, the fourteenth embodimentincludes, as another example of the storage capacitor 70 (see FIG. 1), astorage capacitor 70-14 which is formed of an island capacitiveelectrode 202′ fabricated of an upper conductive layer and a stripedcapacitive line 200′ fabricated of a lower conductive layer as shown inFIG. 31 and FIG. 32. The pixel electrode 209′ is connected to thecapacitive electrode 202′ via a contact hole 217′ penetrating theinterlayer insulator 216, and the capacitive electrode 202′ is set tothe pixel-electrode potential. The capacitive electrode 202′ is alsoconnected to the drain electrode 204 b of the TFT 30′ through a contacthole 213′ penetrating the interlayer insulator 212. As shown in FIG. 31,the striped capacitive line 200′ has, in each pixel, a wide portion oran upwardly projecting portion (i.e., an upwardly projecting toothedportion in a stripe configuration) covering not only the sourceelectrode 204 b, the gate electrode projecting from the scanning line 3a′, and the drain electrode 204 b but also the data line 6 a′. Inalignment, the island capacitive electrode 202′ has a wide portion or anupward projecting portion (namely, has an L-shaped configuration withthe inner corner thereof stepwise expanding) as shown in FIG. 31. Therest of the construction of the laminate structure remains unchangedfrom that of the thirteenth embodiment.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the fourteenth embodiment does not need the expansionof the non-aperture area of each pixel. By laminating the capacitivelines 200′, and the capacitive electrode 202′ on the scanning line 3 a′and the data line 6 a′ on the TFT array substrate 10, a largercapacitance of the storage capacitor results.

In accordance with the fourteenth embodiment, the capacitive electrode200′ at the predetermined potential is sandwiched between the TFT 30′,the scanning line 3 a′ and the data line 6 a′, and the capacitiveelectrode 202′ at the pixel-electrode potential. The TFT 30′, thescanning line 3 a′ and the data line 6 a′ are free from an adverseeffect through capacitive coupling arising from variations in thepotential of the capacitive electrode 202′, and the capacitive electrode202′ (and the pixel electrode 209 a′) is free from an adverse effectthrough capacitive coupling arising from variations in the potential ofthe scanning line 3 a′ and the data line 6 a′. This arrangementeliminates the need for thickening the first interlayer insulator 212 inan attempt to reduce capacitive coupling.

When the storage capacitor 70 is embedded beneath the pixel electrode209′ as in the thirteenth and fourteenth embodiments, at least one ofthe capacitive line and the capacitive electrode is formed of aconductive, light shielding film, and functions as an embedded lightshielding film defining the aperture area of each pixel. Alternatively,at least one of the capacitive line and the capacitive electrode isformed of a conductive, transparent layer, and an embedded lightshielding film defining the aperture area of each pixel may separatelybe arranged. When the storage capacitor 70 is embedded beneath the pixelelectrode 209 a′ as in the thirteenth and fourteenth embodiments, acapacitive electrode may be sandwiched between a pair of capacitivelines as in the twelfth embodiment. The capacitive line 200′ may beformed in a matrix covering the data line and the scanning line.

A fifteenth embodiment of the electro-optical device of this inventionwill now be described with reference to FIG. 33 and FIG. 34. FIG. 33 isa plan view showing a pixel in a TFT array substrate having a data line,a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 34 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 33. Referring to FIG. 34, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in easy-to-identify sizes and tohelp understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 33 and FIG. 34, elementsidentical to those described with reference to FIGS. 24 and 25 (showingthe eleventh embodiment) are designated with the same referencenumerals, and the discussion thereof is omitted.

In comparison with the eleventh embodiment, the fifteenth embodimentincludes a storage capacitor 70-15 as another example of the storagecapacitor 70 (see FIG. 1) below the bottom-gate type TFT 30′ on the TFTarray substrate 10 as shown in FIG. 33 and FIG. 34. Specifically, anisland capacitive electrode 802 is formed on the TFT array substrate 10,and a capacitive line 800 is opposed to the island capacitive electrode802 with a dielectric layer 801 interposed therebetween. The scanningline 3 a is laminated on the underlayer insulator 12 arranged on thecapacitive line 800. The capacitive line 800 is striped and extendsoutside the image display area, and is set to the predeterminedpotential. The island capacitive electrode 802 is connected to the drainregion of the semiconductor layer 210 a through a contact hole 813penetrating the underlayer insulator 12 and the dielectric layer 801,and is set to the pixel-electrode potential. A plug 3 b′, fabricated ofthe same conductive material (a conductive polysilicon, for example) asthat forming the scanning line 3 a, is formed within the contact hole813. In a plan view in FIG. 33, the capacitive line 800 has, in eachpixel, a wide portion or an upwardly projecting portion as in FIG. 33(i.e., an upwardly projecting toothed portion in a stripe configuration)covering not only the source electrode 204 a, the gate electrodeprojecting from the scanning line 3 a′, and the drain electrode 204 bbut also the data line 6 a′. On the other hand, the island capacitiveelectrode 802 has a wide portion (namely, has an L-shaped configurationwith the inner corner thereof stepwise expanding) as shown in FIG. 33.The rest of the construction of the laminate structure remains unchangedfrom that of the eleventh embodiment.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the fifteenth embodiment does not need the expansionof the non-aperture area of each pixel. By laminating the capacitivelines 800, and the capacitive electrode 802 on the scanning line 3 a′and the data line 6 a′ on the TFT array substrate 10, a largercapacitance of the storage capacitor results.

In accordance with the fifteenth embodiment, the capacitive line 800 atthe predetermined potential is sandwiched between the TFT 30′, thescanning line 3 a′ and the data line 6 a′, and the capacitive electrode802 at the pixel-electrode potential. The TFT 30′, the scanning line 3a′ and the data line 6 a′ are free from an adverse effect throughcapacitive coupling arising from variations in the potential of thecapacitive electrode 802, and the capacitive electrode 802 (and thepixel electrode 209 a) is free from an adverse effect through capacitivecoupling arising from variations in the potential of the scanning line 3a′ and the data line 6 a′. This arrangement eliminates the need forthickening the underlayer insulator 12 in an attempt to reducecapacitive coupling.

A sixteenth embodiment of the electro-optical device of the presentinvention will now be described with reference to FIG. 35 and FIG. 36.FIG. 35 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 36 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 35. Referring to FIG. 36, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in an easy-to-identify sizes andto help understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 35 and FIG. 36, elementsidentical to those described with reference to FIGS. 24 and 25 (showingthe eleventh embodiment) and FIGS. 33 and 34 (showing the fifteenthembodiment) are designated with the same reference numerals, and thediscussion thereof is omitted.

In comparison with the fifteenth embodiment, the sixteenth embodimentincludes a storage capacitor 70-16 as another example of the storagecapacitor 70 (see FIG. 1) formed of a conductive, upper islandcapacitive electrode 802′ and a conductive, lower striped capacitiveline 800′ as shown in FIG. 35 and FIG. 36. The capacitive electrode 802′is connected to the drain region of the TFT 30′ through a contact hole813′ penetrating the underlayer insulator 12 and is connected to thepixel-electrode potential. In a plan view in FIG. 35, the capacitiveline 800′ has a modestly wide portion projecting upwardly in each pixelin a plan view in FIG. 35, covering the source electrode 204 a, the gateelectrode projecting from the scanning line 3 a′, and the drainelectrode 204 b (i.e., the capacitive line 800′ does not project upwardin a wide area, thereby not covering the data line 6 a′ in FIG. 35).Accordingly, the island capacitive electrode 802 has a modestly widearea expanding upwardly as shown in FIG. 35. The rest of theconstruction of the laminate structure remains unchanged from that ofthe fifteenth embodiment.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the sixteenth embodiment does not need the expansionof the non-aperture area of each pixel. By laminating the capacitivelines 800′, and the capacitive electrode 802′ on the scanning line 3 a′and the data line 6 a′ on the TFT array substrate 10, a largercapacitance of the storage capacitor results.

When the storage capacitor 70 is embedded beneath the scanning line 3 a′as in the fifteenth and sixteenth embodiments, at least one of thecapacitive line and the capacitive electrode is formed of a conductive,light shielding film, and thus functions as an embedded light shieldingfilm defining the aperture area of each pixel and as a first lightshielding film for blocking returning light to the TFT 30′.Alternatively, at least one of the capacitive line and the capacitiveelectrode is formed of a conductive, transparent layer, and the firstlight shielding film blocking light to the embedded light shielding filmdefining the aperture area of each pixel and the first light shieldingfilm for blocking light to TFT 30′ may be separately arranged. When thestorage capacitor 70 is embedded beneath the scanning line 3 a′ as inthe fifteenth and sixteenth embodiments, a capacitive electrode may besandwiched between a pair of capacitive lines as in the twelfthembodiment.

A seventeenth embodiment of the electro-optical device of the presentinvention will now be described with reference to FIG. 37 and FIG. 38.FIG. 37 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 38 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 37. Referring to FIG. 38, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in easy-to-identify sizes and tohelp understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 37 and FIG. 38, elementsidentical to those described with reference to FIGS. 24 and 25 (showingthe eleventh embodiment) and FIGS. 29 and 30 (showing the thirteenthembodiment) are designated with the same reference numerals, and thediscussion thereof is omitted.

In comparison with the thirteenth embodiment, the seventeenth embodimentincludes a data line 6 a″ between interlayer insulators 216 a and 216 bover a storage capacitor 70-17 as another example of the storagecapacitor 70 (see FIG. 1) as shown in FIG. 37 and FIG. 38. The data line6 a″ is connected to the source region of the TFT 30′ through a contacthole 218 penetrating the interlayer insulator 216 a and the interlayerinsulator 212, and is formed to partly cover the gate electrode of theTFT 30′ from above in a plan view. The capacitive electrode 202 isconnected to the pixel electrode 209 a′ through a contact hole 217″penetrating the interlayer insulators 216 a and 216 b, and is set to thepixel-electrode potential. In a plan view in FIG. 37, the capacitiveline 200 upwardly expands in a large area in each pixel (i.e., anupwardly projecting toothed portion in a stripe configuration) coveringnot only the source electrode 204 a, the gate electrode projecting fromthe scanning line 3 a′, and the drain electrode 204 b but also the dataline 6 a″ and a portion of the pixel electrode 9 a adjacent to the dataline 6 a″. On the other hand, the island capacitive electrode 202 has awide portion expanding greatly upwardly in FIG. 37 (namely, has anL-shaped configuration with the inner corner thereof stepwiseexpanding). The rest of the construction of the laminate structureremains unchanged from that of the thirteenth embodiment.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the seventeenth embodiment does not expand thenon-aperture area of each pixel. By laminating the capacitive lines 200,and the capacitive electrode 202 on the scanning line 3 a′ and the dataline 6 a″ on the TFT array substrate 10, a larger capacitance of thestorage capacitor results.

An eighteenth embodiment of the electro-optical device of the presentinvention will now be described with reference to FIG. 39 and FIG. 40.FIG. 39 is a plan view showing a pixel in a TFT array substrate having adata line, a scanning line, and a pixel electrode formed thereon in theelectro-optical device. FIG. 40 is a cross-sectional viewdiagrammatically showing a connection of layers through contact holesand a laminate structure forming a storage capacitor in theelectro-optical device of FIG. 39. Referring to FIG. 40, the layers andelements are not necessarily drawn to scale and are changed in relativeposition to show the layers and members in easy-to-identify sizes and tohelp understand the connection of contact holes, and the laminatestructure forming a storage capacitor. In FIG. 39 and FIG. 40, elementsidentical to those described with reference to FIGS. 24 and 25 (showingthe eleventh embodiment) and FIGS. 37 and 38 (showing the seventeenthembodiment) are designated with the same reference numerals, and thediscussion thereof is omitted.

In comparison with the seventeenth embodiment, the eighteenth embodimentcan include an island capacitive electrode 202′ formed of a conductive,upper layer and a striped capacitive line 200′ formed of a conductivelower layer, as shown in FIG. 39 and FIG. 40. The pixel electrode 209 a′is connected to the capacitive electrode 202′ via a contact hole 217″penetrating the interlayer insulators 216 a and 216 b, and thecapacitive electrode 202′ is set to the pixel-electrode potential. Thecapacitive electrode 202′ is connected to the drain electrode 204 b ofthe TFT 30′ via a contact hole 213′ penetrating the interlayer insulator212, thereby forming a storage capacitor 70-18 as another example of thestorage capacitor 70 (see FIG. 1). In a plan view in FIG. 39, thecapacitive line 200′ upwardly projects in a large width in each pixel(i.e., has an upwardly projecting toothed portion in a stripeconfiguration) covering not only the source electrode 204 b, the gateelectrode projecting from the scanning line 3 a′, and the drainelectrode 204 b but also a major portion of the data line 6 a″ and aportion of the pixel electrode 9 a adjacent to the data line 6 a″. Thecapacitive line 200′ also has a neck portion at the bottom of thelargely projecting toothed portion between a contact hole 213′ and acontact hole 218, thereby being clear of the contact holes 213′, 217,and 218. The island capacitive electrode 202′ has an upwardly extendingwide portion as in FIG. 39 (namely, has an L-shaped configuration withthe inner corner thereof stepwise expanding). The rest of theconstruction of the laminate structure remains unchanged from that ofthe seventeenth embodiment.

Unlike the conventional art, in which the capacitive line runs alongsidethe scanning line, the eighteenth embodiment does not need the expansionof the non-aperture area of each pixel. By laminating the capacitivelines 200′, and the capacitive electrode 202′ on the scanning line 3 a′and the data line 6 a″ on the TFT array substrate 10, a largercapacitance of the storage capacitor results.

When the storage capacitor 70 is embedded between the scanning line 3 a′and the data line 6 a′ as in the seventeenth and eighteenth embodiments,at least one of the capacitive line and the capacitive electrode isformed of a conductive, light shielding film, and thus functions as anembedded light shielding film defining the aperture area of each pixel.Alternatively, at least one of the capacitive line and the capacitiveelectrode is formed of a conductive, transparent layer, and the embeddedlight shielding film defining the aperture area of each pixel mayseparately be arranged. When the storage capacitor 70 is embeddedbetween the scanning line 3 a′ and the data line 6 a′ as in theseventeenth and eighteenth embodiments, a capacitive electrode may besandwiched between a pair of capacitive lines as in the twelfthembodiment.

When the bottom-gate type TFT is employed as a pixel switching TFT as inthe eleventh embodiment through the eighteenth embodiment, the pixelelectrode and the data line may be formed of the same conductive layer.In this case as well, a variety of storage capacitors may be formedbetween the pixel electrode and the TFT, and the positional relationshipbetween the capacitive line and the capacitive electrode may be invertedupside down. A capacitive electrode may be sandwiched between a pair ofcapacitive lines.

The general construction of the electro-optical device in each of theabove embodiments will now be described with reference to FIG. 41 andFIG. 42. FIG. 41 is a plan view showing of the TFT array substrate inthe electro-optical device of each embodiment with the elements formedthereon, viewed from a counter substrate 20. FIG. 42 is across-sectional view of the TFT array substrate taken along line H-H′shown in FIG. 41.

Referring to FIG. 42, the TFT array substrate 10 can be provided with asealing material 52 along the edge thereof, and a third light shieldingfilm 53 as an outline defining the periphery of an image display area 10a, fabricated of the same material as that of the light shielding film23, or fabricated of a different material, extends along the internaledge of the sealing material 52. A data line driving circuit 101 fordriving the data line 6 a by supplying thereto an image signal at apredetermined timing, and external-circuit interconnect terminals 102are arranged on one side of the TFT array substrate 10, external to thearea of the sealing material 52, and scanning line driving circuits 104for driving the scanning line 3 a by supplying thereto a scanning signalat a predetermined timing are arranged on two sides of the first side ofthe TFT array substrate 10. If a delay in the scanning signal suppliedto the scanning line 3 a presents no problem, the scanning line drivingcircuit 104 may be mounted on one side only. Data line driving circuits101 may be arranged on both sides of the image display area 10 a.Arranged on the remaining one side of the image display area 10 a of theTFT array substrate 10 is a plurality of wires 105 for connecting thescanning line driving circuits 104 mounted on both sides of the imagedisplay area 10 a. A conductive material 106 for electrically connectingthe TFT array substrate 10 to the counter substrate 20 is mounted atleast one corner of the counter substrate 20. Referring to FIG. 42, thecounter substrate 20 having almost the same outline as that of thesealing material 52 shown in FIG. 42 is bonded to the TFT arraysubstrate 10 through the sealing material 52.

Besides the data line driving circuits 101 and the scanning line drivingcircuit 104, the TFT array substrate 10 may be provided with a samplingcircuit for applying the image signal to the plurality of the data lines6 a at a predetermined timing, a precharge circuit for supplying aprecharge signal at a predetermined voltage level to the plurality ofthe data lines 6 a prior to the application of the image signal, and atest circuit for checking the quality and defects of the electroopticdevice in the middle of the production or at the shipment thereof.

In each of the embodiment described with reference to FIG. 1 throughFIG. 42, the data line driving circuit 101 and the scanning line drivingcircuit 104 may be electrically and mechanically connected to a driverLSI mounted on a TAB (Tape Automated Bonding board), through ananisotropically conductive film arranged about the TFT array substrate10, instead of mounting the data line driving circuit 101 and thescanning line driving circuit 104 on the TFT array substrate 10.Arranged on the light incident side of the counter substrate 20 and thelight exit side of the TFT array substrate 10 are respectively polarizerfilms, retardation films, and polarizer means in predetermineddirections to work with operation modes, such as a TN (twisted nematic)mode, a VA (Vertically Aligned) mode, a PDLC (Polymer Dispersed LiquidCrystal) mode, or normally white mode/normally black mode.

When the electro-optical device of each of the above embodiments isincorporated in a projector, three panels of the electrooptic devicesare used as RGB light valves, and each light valve receives therespective color light separated through RGB color separating dichroicmirrors. In each of the above embodiments, the counter substrate 20 isequipped with no color filter. Optionally, an RGB color filter may bearranged in a predetermined area facing the pixel electrode 9 a havingno second light shielding film 23, on the counter substrate 20 alongwith a protective film. In this way, the electro-optical device of eachembodiment is applicable in a direct viewing or reflective typecolorelectro-optical device, besides the projector. Microlenses may bearranged on the counter substrate 20 on a one microlens to one pixelbasis. A color filter layer may be formed of a color resist beneath thepixel electrodes 9 a facing the RGB on the TFT array substrate 10. Inthis way, condensation efficiency of the incident light is increased,and an electro-optical device providing a bright image results. Bylaminating interference layers having different refractive indexes onthe counter substrate 20 and taking advantage of interference of light,a dichroic filter for creating the RGB colors is formed. The countersubstrate with such a dichroic filter equipped makes an even brighterelectro-optical device.

It is to be understood that the present invention is not limited to theabove-referenced embodiments, and various modifications are possiblewithin the scope and spirit of the present invention. Further, it shouldbe understood that electro-optical devices with such modifications fallwithin the scope of the present invention.

An electro-optical device of the present invention heightens theaperture ratio of pixels while increasing the capacitance of a storagecapacitor. The electro-optical device presents a high-quality image freefrom cross-talk and ghosting, and may be used as a display device for adiversity of apparatuses. The electro-optical device may be used as adisplay device forming a display unit of a liquid crystal displaytelevision, a viewfinder type or direct monitoring type video cassetterecorder, a car navigation system, an electronic pocketbook, anelectronic tabletop calculator, a word processor, a workstation, amobile telephone, a video phone, a POS terminal, an apparatus having atouch panel and the like.

What is claimed is:
 1. An electro-optical device, comprising, above asubstrate: scanning lines and data lines that intersect with each otherto form a grid-like pattern; thin-film transistors, each of thethin-film transistors being disposed in correspondence withintersections of one of the scanning lines and one of the data lines;pixel electrodes respectively being disposed in correspondence with tothe thin-film transistors; and a storage capacitor laminated below theeach of the scanning lines, the storage capacitor including apixel-potential capacitive electrode electrically connected to the pixelelectrode and being at a pixel-electrode potential, a fixed-potentialcapacitive electrode being at a predetermined potential, and adielectric layer disposed between the pixel-potential capacitiveelectrode and the fixed-potential capacitive electrode.
 2. Theelectro-optical device according to claim 1, the thin-film transistorincluding a gate electrode that is formed of part of the scanning lineand located over a channel region thereof.
 3. The electro-optical deviceaccording to claim 1, the thin-film transistor including a gateelectrode formed of part of the scanning line and located below achannel region thereof.
 4. The electro-optical device according to claim1, a gate electrode of the thin-film transistor being formed of the sameconductive layer as the conductive layer forming the scanning line. 5.The electro-optical device according to claim 1, the gate electrode ofthe thin-film transistor being formed of a conductive layer differentfrom the conductive layer forming the scanning line.
 6. Theelectro-optical device according to claim 1, the pixel-potentialcapacitive electrode being located over the fixed-potential capacitiveelectrode.
 7. The electro-optical device according to claim 1, thepixel-potential capacitive electrode being located below thefixed-potential capacitive electrode.
 8. The electro-optical deviceaccording to claim 1, an interlayer position of the pixel electrodebeing located over the scanning line on the substrate.
 9. Theelectro-optical device according to claim 1, an interlayer position ofthe pixel electrode being located below the scanning line on thesubstrate.
 10. The electro-optical device according to claim 1, furthercomprising a capacitive line which is connected to the fixed-potentialcapacitive electrode, is formed in at least one of a stripeconfiguration and a grid configuration on the substrate, and is fixed toa predetermined potential outside an image display area.
 11. Theelectro-optical device according to claim 10, the capacitive line beingformed of the same conductive layer as the conductive layer forming thefixed-potential capacitive electrode.
 12. The electro-optical deviceaccording to claim 10, the capacitive line being formed of a conductivelayer different from the conductive layer forming the fixed-potentialcapacitive electrode.
 13. The electro-optical device according to claim1, the pixel-potential capacitive electrode being formed of an islandconductive layer electrically connected to the pixel-electrodepotential.
 14. The electro-optical device according to claim 13, furthercomprising a barrier layer disposed between the thin-film transistor andthe pixel electrode, the barrier layer being electrically connected tothe pixel-potential capacitive electrode.
 15. The electro-optical deviceaccording to claim 14, junction of the island conductive layer with thebarrier layer being formed in a region corresponding to the data line.16. The electro-optical device according to claim 14, junction of thebarrier layer with the pixel electrode being formed in a regioncorresponding to the data line.
 17. The electro-optical device accordingto claim 1, the fixed-potential capacitive electrode being laminatedbetween the scanning line and the pixel-potential capacitive electrode.18. The electro-optical device according to claim 1, the pixel-potentialcapacitive electrode being laminated closer to the scanning line thanthe fixed-potential capacitive electrode is laminated to the scanningline.
 19. The electro-optical device according to claim 1, thefixed-potential capacitive electrode including a portion, laminatedbetween the scanning line and the pixel-potential capacitive electrodein a region running along the scanning line on the substrate, and aportion, laminated between the data line and the pixel-potentialcapacitive electrode in a region running along the data line on thesubstrate.
 20. The electro-optical device according to claim 1, at leastone of the pixel-potential capacitive electrode and the fixed-potentialcapacitive electrode having a light shielding property.
 21. Theelectro-optical device according to claim 20, the one of the capacitiveelectrodes having the light shielding property containing a refractorymetal.
 22. The electro-optical device according to claim 20, the one ofthe capacitive electrodes having the light shielding property coveringat least a channel region of the thin-film transistor.
 23. Theelectro-optical device according to claim 22, the one of the capacitiveelectrodes having the light shielding property being located below thethin-film transistor on the substrate, and being formed of a conductive,lower light shielding film covering at least the channel region on thesubstrate if viewed from the substrate.
 24. The electro-optical deviceaccording to claim 23, the scanning line, the data line, and thethin-film transistor do not extend beyond a formation area of the lowerlight shielding film on the substrate in a plan view.